Before you begin:  

Your phone needs to be powered up and connected to a Local Area Network (LAN) that is able to connect to the internet.

Your computer needs to be on the same LAN as the phone.  

1.  Find the IP address of the phone.   

Press the menu button.  On most Grandstream phones, this is the Circle button surrounded by arrow buttons.  Use the arrows to navigate to the STATUS page.  Select NETWORK STATUS.  The IPv4 address displayed here is your phone's LAN address.

2.  Log into the phone.

Type the IP address of the phone into the address bar of a browser.  Google Chrome, Firefox, Opera, or Safari.  Internet Explorer or Microsoft Edge are not recommended.  On the login page, use admin for the user name and admin for the password.

3. Enter the registration information into Account 1.  Hover over the ACCOUNTS tab and select Account 1>General Settings

Open another tab in your browser and log into your PBX.  Go to Extensions>Modify Existing Extension and click on the extension name that you will be registering this phone to.  Select the SIP & Dialing tab.   if this is a Protelity Hosted PBX extension, note the Phone Provisioning number and then select and copy the SIP Extension Provision Password (ctrl>C or right-click>Copy)

Go back to the browser tab for the phone.  On the first line, make sure the account is activated.  On the second line, put any desired text in the Account Name field.  The text you enter here will display next to the line buttons in most phone models.  In the SIP Server field, enter the IP address of your PBX, or the domain name of your hosted PBX server.  Leave the next 4 fields blank.  In the SIP User ID field, enter the Phone Provisioning Number you noted from the previous step, or just the 3 or 4 digit extension number if this phone is registering to a Protel LTS PBX.  Repeat this same data in the Authenticate ID field.  Now, paste the password you copied in the previous step into the Authenticate Password field.  Enter anything you want into the Name field.  Enter 98# into the Voice Mail Access Number field.  Press the Save and Apply button at the bottom of the screen. 

Your phone should now register to the PBX.  To check this, click on the Status tab at the top of the screen.  You should see something like this:

You also need to verify that your PBX also shows that the phone has registered.  On a Protel LTS PBX, click on the PBX link on the right side of the top black menu and select STATUS.  On a Protelity Hosted PBX, select SIP Peer Status from the Maintenance tab.  The extension you just registered should have an entry similar to this:

4.  Additional important step:

In the Phone, got to Accounts>Account 1>Network Settings.  Set the NAT Traversal option to Keep-Alive