Users will navigate to a webpage where you have the Jabber Guest plugin in place, or they'd click a provided link and it would send them to the VCS-E or Expressway-E to and using reverse proxy, communicate to the Jabber Guest server.
You'll need A records with associated FQDN pointing to your VCS-E or Expressway-E for Jabber Guest to use. No SRV records are not needed.
Highly suggest you look over the install guide I linked to above, it has everything you need to set up Jabber Guest.
Refer to the network topology on pg 25 of the deployment guide I linked to earlier for how the Jabber Guest server is supposed to be installed within your network depending on how your environment is setup.
It's only recommended to deploy Jabber Guest directly to CUCM in a lab environment to familiarize yourself with Jabber Guest. Any other time, Jabber Guest should be deployed with Expressway.