Okay so I want to loose weight, and first thing thatt came to my mine is bike rideing because I enjoy it. If I went out biking how long would I have to do it for? Hour?
You're on the right track. At first, do whatever you can comfortably. Then start building on time. If you can only do 30 minutes to start, then start with that & gradually work up to an hour per work-out. Also toss in a brief warming up & cooling off period of time at slower speeds.
Don't worry about how far you've gone or how fast you've gone. That will come with time. What you should concentrate on is that magic word called 'cadence'. Cadence is the rpm of the pedals. Try to maintain 70 - 90 rpm by up-shifting or downshifting into the right gear using moderate pedal pressure. If pedaling becomes difficult, downshift. Too easy, up-shift.
It's a great exercise for losing weight but it depends on how hard you work at it. Start out with and easy 10 min warm up and then start pedaling at 70-90 rpm's in a gear that is easy to spin but gets your breathing to the point where you can still talk but not sing. Work you way up to a hour or more. It takes time to get your body use to the exercise and burning lots of calories. You burn about 35 calories per mile so the better shape you are in the more calories you burn per hour. You get bonus points for a head wind and hills. Never stop pedaling your leg muscles help to pump blood back to your heart.