To join or create a guild, you need to access the guild functionality in the game, located at the top of your client. Clicking on the guild tab will open the guild menu, as the image below suggests.
To create a guild, you only need to choose a valid name and click the Create Guild button. Upon successfully creating a guild, you will be prompted to relog into the game for the changes to take effect.
After creating your guild, the main tab you will see is the General tab. The General tab contains the most important information about your guild, as shown in the image below.
In the Members tab, you can see all the current members of your guild, as well as basic information about them, such as name, level, class, rank, and their online status represented by a green skull (online) or red skull (offline).
In the Ranks tab, you can see the permissions that each of the existing ranks have, as well as edit what each rank can do and even create new ranks. If you do not have permission to edit ranks, you will not see this tab.
In the Inbox tab, you can see the activities that have been logged in the guild interface, such as members who joined, members who left or were expelled, war notifications, and many others.
To invite players, you need to invite a player or accept someone who has applied. To invite a player, you need to be near their character. Once you are, right-click or ctrl + right-click on the character and click Invite to guild.
If you do not have a guild, you can open the guild menu, in the Top Guilds tab, and see many guilds available for you to apply to. If you apply, the leaders and vice-leaders will decide whether or not they want you to join and may reject your application without reason. Press the Send Join Request button, and a notification will be shown to the leaders and vice-leaders.
If you are invited to a guild, a notification will be displayed in the Inbox tab, as shown in the image.