How may I access the DHCP settings? Want to make printer a FIXED IP

The Nokia gateway nor the Arcadyan gateway appear to provide any static IP exclusions it seems. I have not had any issues with the printers I have here with dynamic addresses so I have not bothered to mess with it. All my devices have obtained IP addresses 101 or higher. That being said the only fixed exclusion to the DHCP range that I can see is the router IP .1 so you might be able to just make the static address setting to the printer below 100 and it could be fine. If you have an IP conflict with the static entry then you will know. I have a record of 24 device IPs for clients on my LAN and 15 to 16 active most of the time and none have an IP below 101. T-Mobile only officially supports 64 hosts on the LAN. The router shows 128, i know, but the official documentation shows 64. You don't need a scope larger than what is intended to support the client supported.

Ping the broadcast address 192.168.12.255 and then show the ARP table for the client. This is simple enough to do. With a Windows client open the terminal, PING the broadcast address, then issue the command arp -a and review the ARP entries the client reports. I run Windows, Apple, and Linux clients and all seem to respond when I ping the broadcast address so it is pretty reliable way to know what clients are active and responding to have a listing. You can get an application to run a ping sweep of the LAN to do the same thing. With a packet capture you should be able to see the lease duration provided. I have not bothered as I have not seen any churn in the IP addressing of the clients on the LAN. If it isn't broke I don't go fixing it.