ee is part of the FreeBSD base installation, so no additional steps are required.
Starting to edit is as simple as typing
if you would like to create or edit a specific file.
Inside the editor, the available commands are displayed at the top. The ^ should be read as Ctrl so, for example, the (escape) menu can be opened by pressing Ctrl-[. This menu allows you to leave the editor (you will be offered to save your changes if you made any) and perform file operations, such reading or saving files.
For more information, check the man page: