Have you confirmed that you have the correct clutch? Either side by side with the old one or on the input shaft...
Also, any lip on the flywheel face? If so, the clutch won't sit flush, then the pressure plate won't bolt up true, and the whole think will jam solid.
Everything off, find a suitable socket to fit the hole on the end of the crank. Offer clutch up, position approximately central, but certainly within the recess of the flywheel. Then locate pressure plate on its dowels and get the bolts started...
Insert socket with long extension and you should be able to tweak the clutch plate as required.
Once satisfied it's central, nip up the pressure plate bolts in an even fashion, quick double check of the clutch plate position and torque the bolts up.
Make sure the box is in gear and offer it up, rocking the output shaft until it catches, the shove the box home onto its dowels and get the rear mounting bolts started.
Have a well earned cuppa and get the rest bolted up