How can I join an alliance?

You'll notice there are several alliances here.
You can either create your own or join one of the existing alliances that are already established.
You'll learn in time that an alliance can offer you brotherhood, guidance and safety. The only way to join an alliance is to request to join one (you will not receive an invitation).
To request to join an existing alliance, or create your own alliance, simply go to the Alliance link and select one in the list or create a new one where you will be the Alliance Master. You need to be 3 days account to create one.