Do you mean the cedilla under the 'c' - comme ça? Depends what system you are using, but if you check through the Lawless French site, there are directions on how to produce the accents; there will also be references to material in questions in the forum to search through. I use a Mac, and it is easy to do directly from the keyboard by holding the letter down until symbol choices appear and then selecting the appropriate number key.

On a Windows computer there are several possibilities to write the letter ç (or Ç). The one I use is to hold down the Alt-key while typing the numbers 0231 (ç) or 0199 (Ç) on the numeric keypad. It works only, if you type the numbers kn the numeric keypad, not the main keyboard. 

The most logical way though is compose key. You press the compose key (or compose key combination) and then a series of characters.

The brilliant thing is the sequence of characters isn't a hard to remember number like the Unicode value (as with alt+keypad or rote learning locations (as with altgr+key). Why does alt gr+a produce æ but alt-gr+o produces ø?

The compose key means you can type like:

compose /o -> ø

compose c , -> ç

compose , c -> ç

compose a ' -> á

compose e ` -> è

compose " i -> ï

compose o e -> œ

compose s s -> ß

compose o c -> ©

compose = c -> €

compose m u -> µ

compose 3 4 -> ¾

What is the compose key? On Linux, by default, you can use the combination shift+alt gr. On other systems, you might need additional software.