Parking is at the Bowderstone car park on the Borrowdale Road at NY 254169; please don't try to park anywhere else. 
Registration is some distance away at NY 250168.  You will be able to leave spare clothing at registration. 
From the car park you can either:
a) Walk or cycle along the road back towards Keswick, over the bridge at Grange, and then south along the track signed to Hollows Farm and Campsite to registration.  About 25 mins easy walk. 
b) Follow tapes from the car park down to the river and along to a shallow place where it is easy to paddle across.  This will get you to registration in about 5 mins.  Most of the time the river is easy to cross, and no more than 30cm deep.  However this shouldn't be attempted if the river is in spate.  If the river is too high to allow people to cross safely on the day of the event then the route won't be taped and you shouldn't attempt to cross.