well I bought the Line 6 ux2 a few ago and started messin' around with it checking the different options with my guitar etc. and after an hour I got a pretty good sound out of it.
i got couple of questions:

1. how do i get the best out of the line 6 ux2?
2. how do i get good quality recordings from this interface in FL Studio.

and i also got some questions about FL Studio (Fruity Loops):

1. any tips on mixing and mastering with FL Studio?
2. what is the best way to record an electric guitar/bass in FL Studio

Select and insert on a channel in the
Mixer -> Hit record -> record as audio clip then record your guitar

After you record if you want to assign it to a different track select the audio track them go to mixer find new channel you want and go CTRL+L

That sets you up. If you want to use amp sims you will probably want to monitor on the initial track. Then if you are using a different track for mixing (for some reason i record everything on track 13 then move them to other tracks cause im weird) you will want one there also.