Hi i'm new to cycling and the forum...not sure what to say really.

I've decided i need something fun and something to get me fit, i'm a bit out of shape really and not pleased about it. I have a 3 year old and i'm a full time mum and part time University student so i don't have a lot of time to work out or anything like that. I really enjoyed cycling when i was young and used my bike to get about (to school, work and on a paper round) and i can't drive so i thought getting a bike would be perfect.
I bought myself a hybrid bike because i plan to use it mostly in town - it's a Carrera Subway 1.

I've not riden much in about 4 or 5 years so i'm out of shape and my legs are all wobbly - any recommendations for how much/far i should start cycling.

thanks.

k.