You can only create a guild if you are not already in a guild. Tap the Guild widget and choose the CREATE NEW option. Create an emblem and give a name for your new guild.

When in the guild tab, you can access your guild's control panel and member list by tapping the small green info button. There you can change settings for your guild:

Tap EDIT to edit your guild emblem.

Tap the pen icon by the GUILD INFO to tell something about your guild. This info is shown when someone is looking for a guild to join.

Tap the pen icon by the POWER REQUIREMENT to set a requirement to filter your guild from those players whose total POWER is below the requirement.

Tap the pen icon to toggle the GUILD TYPE between OPEN and CLOSED. Open guilds are available for everyone, whereas you need to apply for closed guilds and be accepted by the guild owner.

GUILD MEMBERS shows the current amount of members from the maximum of 20.

At the bottom of the view, there is a list of members. The owner is always at the top, and other members appear in descending POWER order. To remove a member from your guild, tap the member, then tap KICK FROM GUILD from the popup.