MSD distributor cap installation

I am probably the stupidest person alive!

Alright, I have an MSD distributor cap and it didn't come with any instructions. Now, inside the cap, there is this red plastic circle thing. Do I need to remove it to put on the cap? Because it seems like I have to force on the cap to bolt it down and I don't know if I should do that. Is there something wrong with my cap?

sorry for the probably "very easy to answer" question. But.....I'm retarded (tommy boy)

thanks in advance,

aj