This section explains how to setup a microSD card in order to boot your Orange Pi board. You need:

• the file u-boot-sunxi-with-spl.bin;
• the Linux kernel image (uImage or zImage);
• the specific dtb file for the board;
• a root file system.

The first step is to insert the microSD card in your computer and identify it. Usually it should be /dev/mmcblk0. The following steps expect that your SD card is /dev/mmcblk0; if your computer identify the device differently use its name instead of /dev/mmcblk0.
Then create two partitions in your microSD card: the first one is the bootable partition that contains the kernel image, the dtb file and the eventual uEnv.txt file, the second partition contains the root file system. To create the partitions you can use the Linux command fdisk:

$ sudo fidsk /dev/mmcblk0

In order to create the two partitions:

Command (m for help): n                                 # Type n
Partition type:
   p   primary (0 primary, 0 extended, 4 free)
   e   extended
Select (default p):                                     # Press Enter Key      
Using default response p
Partition number (1-4, default 1):                      # Press Enter Key
Using default value 1
First sector (2048-15523839, default 2048):             # Press Enter Key
Using default value 2048
Last sector, +sectors or +size{K,M,G} (2048-15523839, default 15523839): +20M      # Type +20M

Command (m for help): n                                   # Type n    
Partition type:                                           
   p   primary (1 primary, 0 extended, 3 free)
   e   extended
Select (default p):                                       # Press Enter Key
Using default response p
Partition number (1-4, default 2):                        # Press Enter Key
Using default value 2
First sector (43008-15523839, default 43008):
Using default value 43008
Last sector, +sectors or +size{K,M,G} (43008-15523839, default 15523839): # Press Enter Key
Using default value 15523839

Then you have to format the two partitions, the first with a FAT file system, the second with an EXT4 file system. You can use Linux mkfs command:

$ sudo mkfs.vfat /dev/mmcblk0p1

$ sudo mkfs.ext /dev/mmcblk0p2

Now you have to clean the partition table of your microSD card  and write the u-boot-sunxi-with-spl.bin typing these commands:

$ dd if=/dev/zero of=/dev/mmcblk0 bs=1k count=1023 seek=1

$ dd if=<u-boot_path>/u-boot-sunxi-with-spl.bin of=/dev/mmcblk0 bs=1024 seek=8

Now you have to copy in the first partition the kernel image and the specific dtb file for the board (for Orange Pi PC Plus it's sun8i-h3-orangepi-pc-plus.dtb). In order to do that type:

$ sudo mount /dev/mmcblk0p1 /mnt

$ sudo cp -v <kernel_path>/arch/arm/boot/zImage /mnt

$ sudo cp -v <kernel_path>/arch/arm/dts/<board>.dtb /mnt

$ sudo umount /mnt

Since Orange Pi boards don't use by default uEnv.txt file it's suggested to not create it. 
Then you have to copy the root file system and the kernel modules in the second partition with the following commands:

$ sudo mount /dev/mmcblk0p2

$ sudo tar xfvp <root_file_system_path>/<root_file_system>.tar.gz -C /mnt

$ sync

$ sudo chown root:root /mnt

$ sudo chmod 755 /mnt

$ sudo cp -rv <kernel_modules_path>/* /mnt/lib

$ sync

$ sudo umount /mnt

Now you have a bootable microSD card and you are ready to use your Orange Pi board.
There is only a last thing to do: since you don't use the uEnv.txt file, at the first boot  you have to set an U-boot environment variable that contains the instrunctions to execute at the boot. So, at the first boot, type any key to stop autoboot and enter in U-boot command line. Then you have to set the environment variable bootargs and modify the variable bootcmd, executed by default at boot. At the end save the modified environment and boot the board.

=> setenv bootargs console=${console} root=/dev/mmcblk0p2 rw rootwait

=> setenv bootcmd `mmc rescan; fatload mmc 0 0x46000000 zImage; fatload mmc 0 0x49000000 ${fdtfile}; bootz 0x46000000 - 0x49000000`

=> saveenv

=> boot

At the next boots the board will boot automatically. Now you can enjoy your Orange Pi board.

This section is a quick guide to the U-boot command line.  To learn more about specific themes visit the U-boot on-line manual at the site http://www.denx.de/wiki/DULG/Manual.
A very important command is the help command or ?  that prints a list of all possible commands with a short explanation. To see the explanation of one particular command you have to type:

=> help <command>

Other four important commands are printenv, setenv, saveenv and envreset. They respectively print a list of all environment variables, configure an environment variable, save the environment variables to persistent storage and set environment variables to the default settings.
The boot command, instead, is the command executed by default at the boot and it runs the actions setted in bootmcd environment variable. So if you want to customize the boot process you have to modify this environment variable.
Other useful commands are run that runs the commands stored in an environment variable, bdinfo that print the informations about the board and fatload that load binary file from FAT file system.