Depends how it's been put on!
Usually there will be a number of screws (often in the top and bottom of the sill and at both wheelarches) and a polyurethane sealant like Sikkaflex.
Find and remove the screws. If the thing doesn't fall off use a hair dryer or suchlike to warm up the join and slowly, slowly cut through the sikka with a thin knife. It will take a while.
If there's a (very) friendly bodyshop nearby, they might get it off with one of the amazing vibrating knives some bodyshops have.
Expect to do a little damage, but with care it should be minimal.
i dont want to brake it
