Connecting to HP 8620 printer

Well, if you have the manual for the printer that is a good place to start. I don't know how old the 8620 is but if it is 6-7 years old it will probably only support connecting on a 2.4 GHz radio frequency. The gateway has both 2.4 GHz and 5 GHz radios. 1 - 2.4 GHz and 2 - 5 GHz radios. Connecting the printer to a separate 2.4 GHz SSID will probably be necessary. In effect you would need to get into the administrative interface for the gateway, probably using the T-Mobile home internet mobile application. If you have the Arcadyan gateway or the Sagemcon you would need to to it this way.

You would need to add an additional SSID (network name) on the 2.4 GHz radio and also configure it with WPA/WPA2 authentication type. Then the SSID would need a password/passphrase for security. Once that is done and saved then you can get into the printer menu, on the printer, and navigate to network settings and then have it find the new SSID on the 2.4 GHz radio and provide it with the password you configured. If the printer wants to play on the network it should be able to join. You would need to make sure the printer uses DHCP for its address. DHCP is for receiving a dynamic IP address from the gateway. Once the printer connects to the wireless network then the gateway will be able to offer an IP address on the LAN, local area network, so it can communicate.