When you signed up with JVZoo, you were asked if you agreed to the Terms of Service. The terms of service allow JVZoo to automatically become an affiliate for any product that you put in the system. The Terms of Service are located here: https://www.jvzoo.com/legal with the vendor agreement being the relevant Agreement (see section 8)
As for promoting your product, you can find your product located within the JVZoo Product Library here: LINK TO PRODUCT LIBRARY
An affiliate is able to promote in any way they wish, according to your agreement. The affiliate is not required to actually mail out their link in order to get credit as an affiliate for a sale.
We send traffic into our own Product Library as well as offers out to affiliates who requested permission to receive news about offers which are selling.