There are two or three rotatable clips - they look a bit like plastic screws - that you rotate through 90 degrees to release.
You also need to pull the edging along the front door up as this goes over the kick panels. The edging has clips that secure it to the metalbodyowrk - you might break one or two of these (they're tight) but cheap to replace. Then move the kick panels backwards. Be careful with the driver's kick panel - there's a clip moulded into the kick panel (at the top of the end nearest the engine) that you don't want to break.