Chamonix is in France, so you will not be able to use it from the start. You will need to buy a ticket till the border. I suppose you plan to travel Chamonix - Martigny - Zurich? In that case you will need a ticket from Chamonix to Vallorcine. That you can easily buy in Vallorcine.
Then once in Switzerland all you need to do is show your Saver Day Pass whenever a ticket inspector requests it.
No need to book anything. The pass is your ticket.