They do not email you a certificate. It's placed on your account for you to use. You can call them when you are ready to make a reservation and want to use it. Then they will make the res. for you and attach the cert for you.

The hotel and date you are choosing has to have reward availability in order to use it (just like any other reward reservation).

EDIT: I will edit this due to the many responses of this being incorrect information. It appears that some people did receive an email with a cert attached while others did not. The OP stated his account has been credited with the cert.

I am thinking the OP will likely not receive a cert via email. In any event, the cert is logged into your hhonors account whether you received it via email or not. You do not have to take the physical cert w you upon check in. You should have the cert number w you though. If you misplace it just call hhonors and ask them to give you the number, it is noted on your reservation/confirmation once your reservation has been made. This is the same process as making any other points/rewards reservation.