The easiest way to get several devices connected is to get a dedicated simple Ethernet router.
You can find suitable Ethernet routers from very many stores. Please ask for an Ethernet router, or ”wifi router” which does not have additional functions as ”ADSL” or ”Cable modem” or ”3G/4G mobile broadband”. For example, if you go to Multitronic store at Gummeruksenkatu 6 street address and tell them that you need an Ethernet router for the Soihtu network, they should know which type of device to suggest you.
Basic Ethernet router, about 30 euros: https://www.multitronic.fi/en/products/1289414/tp-link-tl-wr841n-2-4ghz--wifi-reititin
For gigabit speed: https://www.multitronic.fi/en/products/3013282/tp-link-archer-c6-v3-2-ac1200-dual-band-802-11ac-gigabit-router-4xlan-1xwan-iptv-mu-mimo