Let me try to give a broad answer.
As a starting place, I will assume use of
Xfinity equipment.
My house has both TV and Internet service. We also have cell phones.
My Internet comes from Comcast and uses the name Xfinity.
The Virginity router has WI-if. It has to be turned on and the password set. Customer service can do it for me or I can do it my sled.
At one time the device was:
http://10.0.0.1
(But recently it was changed. Yours may differ.)
Then I wee a page in my browser that lets me get into the Wireless setup for the router, Once set, it gives both an inherent connection or a wireless to any computer or device in my house. Often we have two Desktops and four smartphones running at the same time. On of the Ethernet connections go out side to another router in my barn. There I have a spare D-Link router with wireless. It is set as an AP thing, that way anybody in the barn can use a smartphone or laptop to get my internet connection.
Your Internet provider can help you with this.