If you are not in a clan, you will see two options in the bottom-right corner of the screen when you are on the Clan or Clan Chat tabs. These options are "Create" and "Join". If you tap the "Create" option, you will be taken to the Create A Clan screen, where you will be presented options to customize your clan.
First, you can enter the name of your clan by tapping the "[name]" box at the top. Names are limited to 16 characters. Note that you will not be able to change the clan name once the clan is created so be sure that you are happy with it before creating the clan.
Next, you can enter a description for your clan by tapping the "[description]" box at the top. Descriptions are limited to 144 characters. You will be able to change this after the clan is created.
Below, you will be presented with 6 sections for where you can customize the logo for your clan. These sections are Icon, Icon color, BG (Background), BG color 1, BG color 2, and Frame color. You can scroll through the options on these sections by swiping up and down when your finger is on the relevant section. You can then tap the option to confirm the change. Any changes made will be shown on the clan logo shown in the top-left corner.
On the right, you will see three more options. These are Recruitment, Min Trophies, and Country. These options can be changed by tapping the arrow buttons on the sides of the options.
With the Recruitment option, you can set it to either "Open" or "Invite Only". Setting this option to "Open" will allow any player to join. Setting this option to "Invite Only" will mean that players will need to send a request that needs to be confirmed by a clan member before joining.
The Min Trophies option allows you to set a trophy amount (up to 20000). Players will then need to have that many trophies or more to be able to join.
Changing the Country option allows you to choose between various languages. This is useful for making players aware of what language is preferred in the clan. This option can be set to "International" if there is no preference.
Once you are happy with your clan, you can confirm the creation by tapping the button in the bottom-right corner. This can only be done if you have 10000 Cash and will cost this much to create.