What do you mean precisely ? Post screenshots (without personal info) if you wish.

You do not need to activate the pass in order to get reservations.

They can be made on eurail.com (2€ fee per person per train) or most of the time through the railway companies directly. Have a look at : https://www.seat61.com/interrail-and-eurail-reservations.htm

For firther questions, please mention the route if you want good advice. :)