This really doesn't have anything to do with Ubuntu, but FCK Editor has some good installation docs if you go to their website. I haven't messed around with it too much, but I am just about to integrate it into my web app called KASL WebHost (at my website).
For the most part, put FCK Editor in whichever directory you need in your website. The rest includes reading the docs at
http://wiki.fckeditor.net/.
For the block of code that you put in your page where the editor goes, you can modify any needed variables to fit your site.
I am sorry that I can't be more detailed, but I replied to this just I can have it watched for me. Doing this allows me to be notified if anyone is still interested. That way, after I get it working in KASL WebHost, I can come here and help out