Bushing trouble

I bought a bushing kit for my 63 Valiant from Mancini Racing and when i got them they are the polyurethane bushing and i was wanting to find out how to to put them in because the little ones go in fine but the big bushing is so hard,What do i need to do to soften them up to push them in,I took the inner sleeve out like it said but i thought when i ordered them it was suppose to be the oem ones but got these,Has anybody else had any trouble with them,Thanks for any help.