There are three ways of interfacing with your board: over serial, with a keyboard and monitor, and over the network.
The preferred method is to interact with it on its first boot through serial, just because it's the method through which you'll be most likely to debug any early boot failures. However, any of the other two methods should work in the best case as well, and are usually easier to set up.
Methods Of Interacting With The Board
Interacting Through Serial
To get a serial connection to the board, you'll need a 1.5 megabauds capable 3.3V serial adapter, such as the PINE64 Woodpecker.
Connect GND of the serial adapter to a ground pin of your board. Then, connect the TXD pin of the serial adapter to the RXD pin of the board (pin 10), and the RXD pin of the serial adapter to the TXD pin of the board (pin 8). If this doesn't work, try swapping TXD and RXD around, sometimes the labelling is reversed.
Please ensure that the board is turned off and unplugged while connecting the serial adapter, to avoid any risk of shorting out something by accident.
Plug the USB to Serial adapter into your computer, and open a serial
terminal at 1500000n1. On linux you can do it like this with picocom:
picocom -b 1500000 /dev/ttyUSB0
On Windows, you can use a serial terminal like PuTTY.
Interacting Through Monitor & Keyboard
To interact with your board through monitor and keyboard, just connect a normal USB keyboard to the board's USB ports and a monitor capable of displaying a 1920x1080@60Hz (or 1280x720@60Hz) signal.
Please note that you will not see messages from u-boot this way, the video output only becomes functional once the Linux kernel is started and sets a video mode.
Interacting Through Network
The board will grab an IP through DHCP on any available wired network adapter and start an OpenSSH daemon on port 22 (the default). It'll also announce itself over mDNS.
This means connecting to the board is as simple as plugging in a network cable and ssh'ing to firstname.lastname@example.org, where hostname depends on your board and is one of the following choices:
Alternatively, you can connect to the board's IP directly, though you'll need to find said IP yourself.
After connecting power, please allow a few seconds for the board to boot. It's busy resizing your root partition and file system to take up the entirety of the SD card or eMMC module.
Once you hit a login prompt, use the username pleb with the default password pleb to log in. You will be immediately asked to change your password. If you're connecting over SSH, this means you'll have to log in again with your new password after completing the password change.
Please be aware that there is no ability to log in as root for security
reasons; instead, use
sudo -i to get a root shell when running
as the user pleb.
Now that you've booted the OS and logged in, you're probably eager to install some software. That's why it's highly recommended you read the page about software choices to be aware of some hardware specific pitfalls.