Start by having a pedal out to Watch Hill/Setmurthy, beyond the school – here
There are loads of short criss-crossing trails, from fairly mean DH to rootsy XC.
Go into 4Play Cycles and talk to Stephen or Adam (eve rides on Tuesdays)
Follow the C2C route out to Wythop and then use the BWs to access Wythop woods and into Whinlatter – here
Half an hour on the road gets you access to Skiddaw and the Back o’ Skiddaw – Most trails here are pretty good
Head to Lorton and over the Mosser fell roads to access the lovely BWs around Loweswater
Edit – did you mean CX or MTB? Advice above good for both really
Offer a friendly local beer and I’m sure they’ll show you on a map or act as guide…….