If you search this forum you can find out how to push back and cock the ejectors one at a time. The corner of a wood workbench works, but be careful. Those springs are strong. The hammers must also be cocked to install the forend. You can also fing how to do that here. Needless to say, but I will, never try to force on a forend and always press down behind the latch, to avoid breaking the wood.
If you have any problems, a good double gun smith is a lot cheeper than a replacement for- end.
http://parkerguns.org/forums/showthr...jector+cocking
Also, if the firing pin hammers are uncocked, see B Dudley's response #5 to this thread:
http://parkerguns.org/forums/showthr...hlight=ejector
Best,
Patrick Butler