Museum Access in Paris-- how to make reservations?

You can make reservations by going to the website of the museum you want to visit. The website will have a button that says “tickets”, click on it and it will take you to the screen where you can select date and time of your visit and number of tickets. You pay and you can download your tickets. That’s it.

thank you-- I bought theParis Museum pass, and now when I go to the website it wants to charge me for tickets. I do not think I can refund my museum pass

The Louvre, for instance, has a button for pass holders:
https://www.ticketlouvre.fr

I a trying to get into Musee D'Orsay and I do not see this option to put my pass number?

It would have helped if you had mentioned the Paris Museum pass in your post. Just like it helps if you would state what museum you’re trying to book. Many museums offer the possibility to “buy” a free ticket. This means you book a time slot, but don’t have to pay anything. At the entrance you show both you free ticket with the date and time and your museum pass.

We are interested in D'Orsay, Picasso, Rodin mostly. I cannot find any way to reserve entry at D'Orsay without purchasing tickets.

You don’t need to book a time slot for the Orsay. Their website clearly says so; “ Holders of a Paris Museum Pass or of a ticket purchased from a third-party vendor do not need a time slot reservation.”
Source; https://billetterie.musee-orsay.fr/en-GB/products?famille=1933737738230400130

Thank you-- I much appreciate your helpful advice! I will now try to buy a free ticket :)

Oh I see no reservation required at D'Orsay-- thank you