If you're wanting to clean a certain mod you dont need to load the whole list. You just load the mod that needs cleaning. IE click the whole list select the 'select none' option and then just click the one needing cleaning. TESV Edit will load any other plugins that are masters of the one needing cleaning itself. To add FNIS as an executable, it tells you later how to do it, but essentially you do the usual add as executable like you did for Wrye Bash etc and in the 'binary' field, point it towards the FNIS for users exe.