Hello!
At the beginning, I would like to point out that in technical matters I am a layman, so the problem can be very simple, but I have not found a solution anywhere.
Well: in the apartment that he rents, there is internet with UPC, which has such a base in the wall:

(2 cables come out of it - one is plugged into the router, the other is loose, previously it was plugged into a TV modem that no longer exists)
In addition, there is a socket next to this base:
.
Throughout the apartment, in the walls there are the same sockets as the one above + internet sockets next to them (such as the RJ45 plug) with the inscription "Internet". And now my question is how to make these sockets in the wall have internet?
At the beginning, I would like to point out that in technical matters I am a layman, so the problem can be very simple, but I have not found a solution anywhere.
Well: in the apartment that he rents, there is internet with UPC, which has such a base in the wall:

(2 cables come out of it - one is plugged into the router, the other is loose, previously it was plugged into a TV modem that no longer exists)
In addition, there is a socket next to this base:

Throughout the apartment, in the walls there are the same sockets as the one above + internet sockets next to them (such as the RJ45 plug) with the inscription "Internet". And now my question is how to make these sockets in the wall have internet?