A ford focus does'nt have a fan belt.It has a auxilary drive belt located on the right hand side of the engine conpartment (driver's side).It has a belt tensioner underneath the power steering pump.Using a spanner turn the tensioner clockwise to release the drive belt tension.The tensioner cannot be adjusted but if it causes problems it can be renewed. The auxilary drive belt usually lasts for about 100,000 miles.If indoubt always renew the belt.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix cars.