Old house - phone line to Ethernet set up

We have an older (1920's) house that I am wanting to wire up ethernet plugs in a couple of the rooms.

The phone line enters the house in the main office in the form of a male plug. What options do I have so that I can convert this to an ethernet wall socket, which in turn will be connected to another wall socket in a another room?

If you could link me to a howto or equipment needed, that would be great.

Thank you