There are a number of ways to add it to your fx bin... If you're using the browser, you can drag it to the bin of an audio track... Or else you can right click in the bin and navigate to it through the list finally selecting it...
A note though... I don't know if it's supposed to be used as a synth. I thought it only an effect but I may be wrong and I can't check at this time...
Another caveat is that you will need to turn on input monitoring for the track as it functions on the output of the track as do all fx...
Keni