This beginner’s program is a great way to start at the gym.

It starts with some cardio to get you warmed up, and then works through all the major muscle groups, using resistance machines rather than free weights, to help you get used to correct form. Adjust the weights so that you reach failure in your third set at around 15 reps. Each session should take about an hour. Complete this program 3-4 times a week, and always give yourself a day’s rest between sessions.

You need an iPhone with Reps & Sets installed to download programs.
If you don’t have an iPhone, you can preview this program here.