When you install ShoreTel Communicator's Mac app, it launches up and asks you for a server name, username, and password. The username and password will be specific to each user, but the server name will likely be the same for everyone, at least at a small- or medium-sized organization.
So if you have Mac clients and some way to distribute profiles to them, you can use a .mobileconfig profile to pre-fill-in the server information. I've posted an example on GitHub, so you can just modify that to fit your organization's needs.
Once that's deployed, when people install ShoreTel Communicator for the first time, the server address will be in already, and they'll just have to fill in their usernames and passwords.