The easiest answer and it is a correct one is
Read the config file
The heart and brains of i3wm is all written down in ~/.config/i3/config.
Follow the video to cover the basics.
Super + F = full screen or focus
and many other shortcuts
Where to find help
- i3wm :
- i3wm is distro independent : any of those tutorials can help you
- Arch Wiki : https://wiki.archlinux.org/index.php/I3