Insert your SIM card > open Nommi app > Profile page > My device > SIM settings > APN settings. 

 

Another way on web admin: 

Connect your phone to Nommi > Copy 192.168.0.1 (or 192.168.173.1) to your browser > Settings(login: admin pass:admin) > Dial-up > Profile Management and set it up there. 

Check instruction in the attachment both for mobile and desktop version.