Ive got that one but with the back box too,
Its easy,
Revers your car onto ramps or over a pit, undo your origanal exhaust at the end of the down pipe, There are 2 bolts ither side that are spring loaded,
between your down pipe & exaust there is a large gasget/ring keep hold of this you need to put it back in when you put it back together,
Your Exhust should now be hanging on its rubbers, Disconect it from the rubbers & it should be off,
Put your new pipe together the same as the origanal useing gasget seal on the joins,
Put your new pipe on in the revers of removel remembering to put the gasget/ring in properly it sits in a grove,
Then nock the back box off your origanal system & clean it up, Put it on the end, I do this last as it is easeyer to position, Check all your clamps are tight & away you go.
Hope this helps.