First make sure you have the latest drivers for your UX1

http://line6.com/software/

Here's a few UX1 set up videos

http://line6.com/support/docs/DOC-2379

http://line6.com/support/docs/DOC-2077

In a nutshell, to get started in Reaper select the UX1 ASIO as your device.

Insert 2 tracks and arm them to record.

On one track select sends 1/2, on the other track select sends 3/4.

In this fashion you will capture both the dry and wet signal. You can add the POD Farm plug-in to the dry signal post processing.

There may be a bit of a learning curve but you can start here

http://wiki.cockos.com/wiki/index.php/Reaper_Documentation

And Reaper also has a pretty good forum.

Although you can record Bass with the UX1, you may want to look into the Bass Expansion pack.