You can add friends to play with using the game identifier (Support ID) that players post on the official Facebook game community here.
To redeem a code, go to the Friends menu → Invite Friends → Add Friends by ID. You can also find your friend code in this tab and share it with other players in the community. The number of invitations you can send is unlimited. Note that you should wait for these players to accept your requests. Only after that will you be able to visit their Albions, send gifts, or communicate with them.