Lots of great advice above. I just got back into cycling last March, since then lost 40 lbs total - lost 10 lbs cycling, the remaining 30 lbs after I joined a gym with a focus on weights and spinning. Over the cold months the spinning definitely made my riding stronger once I went back outside. And it gave me the confidence to finally use cycling shoes, which I was pretty wary of for a long time. It was risk-free getting on and off that spinning bike with the shows throughout the winter - by the time I took those shoes outdoors, I was fine.
Just get out there and ride. And have fun! Find out about the different routes in your area. Talk to people about cycling - maybe find a local club or association.
Some tips from my nutritionist: after a hard work out, eat within the first 20-30 minutes of finishing. Chocolate milk is a good idea after a work out. They actually got me drinking gatorade because I found I was losing my energy for a spinning class after work - it did help me. I had never tasted Gatorade before last year - I don't normally like sugary drinks. Have a balanced diet - eat whole foods, veg, fruit, meats, whole grains. You will need to fuel your cycling.
Bon vélo!
Get on your bikes and ride!
'Bicycle Race' -Queen