A lot of configuration in FreeBSD is done by editing text files. Because of this, it would be a good idea to become familiar with a text editor. FreeBSD comes with a few as part of the base system, and many more are available in the Ports Collection.
The easiest and simplest editor to learn is an editor called ee, which stands for easy editor. To start ee, one would type at the command line ee filename where filename is the name of the file to be edited. For example, to edit /etc/rc.conf, type in ee /etc/rc.conf. Once inside of ee, all of the commands for manipulating the editor's functions are listed at the top of the display. The caret ^ character represents the Ctrl key on the keyboard, so ^e expands to the key combination Ctrl+e. To leave ee, hit the Esc key, then choose leave editor. The editor will prompt you to save any changes if the file has been modified.
FreeBSD also comes with more powerful text editors such as vi as part of the base system, while other editors, like Emacs and vim, are part of the FreeBSD Ports Collection (editors/emacs and editors/vim). These editors offer much more functionality and power at the expense of being a little more complicated to learn. However if you plan on doing a lot of text editing, learning a more powerful editor such as vim or Emacs will save you much more time in the long run.
Many applications which modify files or require typed input will automatically open a text editor. To alter the default editor used, set the EDITOR environment variable. See shells section for more details.