Simple! Use the Fruity effects!
Click on the channel you want reverb on.
See the LCD number in the top right? Move that up to 2 (you can move it up to 16, 1 is the default FX channel)
Double click that number, which will bring you to the effects window. You can also get there by clicking the "FX" button on that toolbar at the top with the 5 large buttons.
Anyways, when at FX channel 2, apply reverb by clicking on the arrow next to an empty slot. Look for "Fruity Reverb" in that list... I think you can figure out the rest. btw the first channel in the effects window is "M" for Master, which means it applies to all instruments
Hope I helped.