All you have to do is present your Pass at the entrance of the museums and monuments you want to visit. The validity of your Pass is calculated from the time of your first visit:

A Paris Museum Pass 2 Days is valid for 48 hours;
A Paris Museum Pass 4 Days is valid for 96 hours;
A Paris Museum Pass 6 Days is valid for 144 hours.

For example: a 2-day Pass activated at 1pm on a Thursday would be valid until 1pm on the Saturday.

No, it is not necessary to book your visits in advance for most of the museums and monuments included. Just, go to the entrance of museums and monuments with your Paris Museum Pass and stand in the line reserved for people with tickets.
 
Exception :
To access the Louvre museum, you must now book a time slot for your visit to Louvre. Booking is free of charge.
Once you have received your Paris Museum Pass :

1. 1. Visit www.ticketlouvre.fr
2. 2. Select ‘Paris Museum Pass holders’
3. 3. Choose the date and time of your visit, then validate and confirm your order
4. 4. Create your customer account and click on ‘Proceed to payment’
5. 5. Indicate the name of each visitor and the serial number of their Pass, click on ‘Payment’
6. 6. Download your tickets (in printable or smartphone format)

No, the Paris Museum Pass only gives you admission to museums and monuments included in it. If you want to have the use of an audio guide or take part in a guided tour during your visit, any supplement will be at your expense.

No, with the Paris Museum Pass you are limited to one entry for each museum and monument included in the Pass.

The majority of museums and monuments are free for children less than 18 years old and for young residents in the EU aged 18 to 25, the Paris Museum Pass is therefore unnecessary. To gain access to the museums and monuments concerned, simply present proof of identity or, if required, collect a free ticket at the entrance.