Some exercise is better than none. That said, one hour a week isn't enough to benefit noticeably.
First, it's a good idea to know what your goal is for going to the gym. Are you trying to lose weight? Build muscle? Train speed? Train endurance? Become more flexible? Be able to stand on your hands or do breakdance? Know what you expect to gain. The more specific your goal, the better. For example, instead of "I want to lose weight" say "I want to lose 10/20/30 pounds." You want your goal to be measurable. Then you can set periodic goals.
Second, find a workout regimen that meets your needs. If you are trying to become faster, slowly jogging on a treadmill over and over isn't going to really help much. If you are trying to build muscle, swimming a lot of laps isn't going to be very useful either. Decide what you want to do, then pick a workout plan that matches. Once you have a workout plan,
follow it consistently. You will gain some benefit from working out sporadically, but if you want real results then you must maintain your workout schedule.
Picking a workout schedule isn't very hard. Take into consideration your goals, time constraints, and distance restraints. If the only gym is a 30 minute drive away and you don't normally get home until 7pm, you may not want to go to the gym everyday. If you want to lose weight, but not necessarily very quickly, you can do fewer workouts per week as long it's consistent.
A sample workout schedule might be:
3 days a week, Monday, Wednesday, Friday
Monday - Run 1/2 a mile, take a 5 minute break. Do this 4 times.
Wednesday - Run 1 mile, take a 7 minute break. Do 3 times.
Friday - Run 1.5 miles, 10 minute break. Do 2 times.
Also incorporate stretching.
Another sample workout would be:
Monday: Work on chest and biceps
Tuesday: Abs and legs
Wednesday: Back and triceps
Thursday: Abs and legs
Friday: 2 mile run
I strongly recommend the book called Body By Design, written by Kris Gethin. It's probably $10-15 on Amazon. He covers a nutrition plan too.
Focusing on your health can take a lot of time. But your health is something you have to live with your whole life, and you only have one body.
If you have any questions for me feel free to shoot me a PM.