Plug the LAN cable into the laptop?

Where do I have to plug this cable into my laptop?

on the right side

Or on the left

does that fit in or how should I put it in

That is probably a notebook without a LAN port. Either use WLAN or purchase a USB LAN adapter.

There's no suitable port on the side… If there's none on the back, it will not have a LAN port

There's no connection for LAN in the pictures.

Has no LAN connection. But there are adapters for it

You need a part like this: https://geizhals.de/...48063.html