I ordered the model that I did because it has a set up for wired cable.
Then plugging in the cable ought to be all you need.
The roku will tell you to go to roku.com and set up an account. But the account is free.
Most channels are free.
There are some channels that charge a one time or monthly fee through Roku. If you want any of the pay channels through Roku, you’ll have to provide a credit card. But I don’t think I have any of those.
There are some channels that have you set up an account at their site, and provide a credit card there. Mog and Netflix are that way.