First of all, configure ONT. We will connect to it through any of the LAN ports, in the browser we will type the address 192.168.1.1 and enter the login and password.
The standard login is admin, the password is admin.
With elevated privileges, login is mgts, password is mtsoao.
The most basic thing is to create a WAN connection with the necessary parameters, in which we indicate the VLAN number, I will use 228.