A tune consists of basic notes and a lot of twiddles.
If you listen very carefully the first time through you should be able to find the basic notes that form the tune ,which you can start playing (quietly). After a number of times through you can gradually introduce the additional notes that form the tune.If you attend sessions on a regular basis you will gradually learn these tunes off by heart, which will then make room for others. If you introduce a new tune to a session ,do not be put off that very few join in. They are going through the same learning process. If after five sessions you are still getting no response from your tune then ,it may be time to move on to another.
Al