1994 Dodge Intrepid My car wont turn on

I am 16 and I bought a 1994 Intrepid as a first car. I like the car I drove the car a few times and loved it, but my car one day did not start after an afternoon sitting in it playing music with the engine not running so altenator wasnt on. But I bought a new battery and put it in and the car worked fine but that battery died and I never even sat in the car or turn it on often. I jumped it and it worked but then the next day it stoped again. The person I bought it from told me it was a short in the car that made it impossible to use the keyless entry but is it the short or the altenator and when I jumped I let it sit for 13 min befor turning it off.