Click the join button for the group you wish to join
If you already have an account a message will be sent to the moderator for the group and they will either accept or decline your join request
If you do not have an account you will be prompted to create a simple account. If you are an Android user the attached photos will show you how the date picker works. Just remember to tap the year first!
Once you have created your account the moderator will receive your join request