In order to get access to family settings, use the "Family Banner" button on your base.

If for some reason there is no banner on the base, you’ll have to make and set it. The banner recipe is available at level 1 and higher. To make a banner you’ll need a log and a stone (easy to find in any location) as well as a rope and fabric (search monsters’ dead bodies). To raise a banner, go to Build mode (a button under the mini-map), then find the banner in the Furniture section.

After interacting with the banner the following actions will be available to you: “Create a family” and “Join a family”.

If you select “Create a family”, a family settings window will appear, where you will be able to invite other players to neighboring lands in order to build a settlement and explore the world together.

If you tap the plus button on the site, the player selection menu will open. The game will pick out several random companions for you (the list can be updated with the dice button). You can also find and invite a specific player by entering their unique digital ID (shown next to player’s name). The "Invite" button will send the player an invitation to the family. As soon as they accept it, the player will join you.

Using the Family Banner, you can also join an already existing family. To do this, select “Join a family” and enter the family's name in the search box. The button "Send request" will send the family leader your request to join their family.
In order to join another family you may have to disband your own family. To do this, use the "Disband" button in the family settings window.