I am not familiar with GrandStream phones at all so I wouldn’t be able to provide you with any guidance but you’ll need to figure out by reading their documentation what they require to be setup for them to automatically know how to pull configuration information from a designated provisioning server.
All SIP phones worth something have a method for automatic provisioning, you just need to find the documentation for your particular hardware and follow it.
In it’s most general form, you configure the phone to provision using a url like this:
http://username:password@host:port
The username and password are as specified in System Admin pro, which if not used are omitted along with the @ character. With port 84, it distills down to
http://pbxip:84
Don’t expose your provisioning services to untrusted traffic.
I can’t as I’m not familiar with that device, but I presume it’s like pretty much like any other IP phone, there is an option somewhere for specifying a URL to provision or download config.
These are SIP server settings only and not provisioning settings. You’ll probably have to do some Googling on how and where to set provisioning settings for your flavor of phone hardware.