Well...sorry about your uncle, but he left you a wonderful present. I will assume you have either a 50mm, or a 35 mm lens,either of which is great to start with, and might serve as your only lens for many months to come.
My suggestion depends upon your previous knowledge, in this case apparently relatively little. First learn about the basics of exposure, etc. by purchasing any one of a number of books for beginners. With the M7 in hand, read the manual and then supplement such with one of the other more specific books that give you more information about "the rangefinder camera" in general, and the M system in particular. One might suggest the book by Easterland on the M7, and Osterloh's book on the Leica M. The latter might be hard to find, but certainly is a classic. Finally, load your M7 ( one might suggest that you pick a good general purpose film with ASA of 200 to 400, and stick with one film for a while )and start to take pictures....many of them, of diverse subjects. Look at the results, and try again. Don't be afraid if your results aren't perfect...take more pictures, and then some more. Within a remarkably short time you will be moderately proficient, and will find yourself bitten by the Leica M lens fever....but that is another story! Best of luck to you, and please let us all know how you are doing.