It is strongly recommended that you find a tribe to join as soon as possible if you are a new player. While it is possible to create your own tribe, we would recommend waiting until you have more experience to do so.
In order to join a tribe you will need to receive an invite, it is not possible to apply via the game interface. To view a list of tribes, you can click on Rankings and then Tribes. However, you may prefer to view tribes that have a strong position on your continent, in which case you should go to Rankings and then Continent Tribes. Most tribes will typically show whether they are recruiting or not on their profile. They will also list the name of the leader or recruitment manager. This is the person you should mail to enquire about an invitation.