If you have not taken any of the ASA courses, you will have to start with ASA level 101, 103 and 104. All three of these courses must be taken aboard a monohull. THEN you move up to 114 ... which is the catamaran course.

You can read about the course requirements here.

In the BVI, it takes 10 nights (with your own private instructor) aboard a monohull to accomplish the first three levels, if you charter a bareboat. I'm not sure about the duration with the various sailing schools that teach groups.

I obviously don't know where you live, but there are many different places where you can take these courses in the US and other parts of the world. You will find all the various places offering courses in the US here.

Hope this helps.