Don't force anything. Nothing in a PC build requires any force. Nice and easy, slowly and efficiently.
Also, not too much thermal paste on the CPU. a small pea sized dab right in the centre will do just fine. The heatsink will then spread it out for you when you apply it.
Also, not too much thermal paste on the CPU. a small pea sized dab right in the centre will do just fine. The heatsink will then spread it out for you when you apply it.