Check CSSU installation guide from this forum. There you will find all the repos. Would suggest to choose testing option cause then you will get some things to work that would not work without it. And put testing repo if you want cutetube 2 to work properly while downloading youtube videos to watch. Atleast I needed that for that as well as for telegram through pidgin (which needs a lot to do if you gonna use it. I can give hints to that if you are about to try it). Opera testing and fennec are my main browsers on use cause have not been able to open many sites with microb.

There are some threads about perfect setup for N900. Search with that.