How do you use a certificate
 

How do you use a ecertificate? I just signed up for a visa and recieved a cat 5 certificate for a one night stay. How do I use it? Can I book it online?

The Visa certificates are now electronic (used to be paper in previous years).

I just used mine. In my case, I was staying multiple nights and combining awards so I did the following:
1. Look online to search for a room but checking the box that says "Use Marriott Reward Points." That will show if there is any availability for your desired property.
2. Call Marriott reservations to book the room, telling them that I will be using the Visa certificate so that it will be linked to the reservation.

You might want to look closely at your e-certificate to make sure what category level it is. Normally, the e-cert for signing up for any version of the Marriott branded Visa cards is only a cat. 1-4. The Cat. 5 certs are received annually starting a year after sign-up (for the Premier card only though.)