If your engine has the hole in the back of the case, then you slide the liner up to expose the hole, turn the engine to align the wristpin with the hole, and slide out the wrist pin. If the engine doesn't have the hole, you have to remove the liner and then 'pop' the rod off the crank.

The modern SuperTigre ringed engines no longer have the hole in the case. When you replace the liner, you have to mount the piston/rod assembly on the crank, align the piston ring so that the ring gap is at the pin in the ring groove, heat the case, and carefully slide the liner down over the piston. You have to make sure the piston's absolutely straight in the liner. The bottom of the liner has a bevel to compress the ring as the liner slides down over the piston. You may have to turn the liner a bit to get the ring to compress. Many other engines go together the same way.