If you have got an undertray then you will need to take that off so check the fixings as people fit all sorts.
Then the only other tool you will need is a long 24mm ring spanner - an aviation spanner is ideal to release the tensioner.
If you have never done one they can be a bit fiddly - a bent wire coat hanger might help to hook the belt around the pulleys, and check the belt run is correct - get it wrong and you will have a foot of slack left in the belt.