D.N.
I use the treadmill and elliptical doing interval speed walking since I cannot run. I walk at a normal pace to warm up for about 3 to 5 mintues and then pick up the speed for 3 minutes then down for 2, up for 1, etc. I do this for 30 minutes or so depending on how much time I have. Also adding either dumbbells/hand weights or a workout cord is good. there are books that can show you some exercises to do with them. Since you have access to a gym, schedule some time with someone to show you the best way to use the equipment for strength training. It should be included in membership at most places.