You must be either the Clan leader or a Clan Co-Leader to assign a member of your Clan to "Clan Co-Leader"
To promote a member:
Enter Clans
From the list of Clan members on the left side of the screen, click the blue arrow to the right of the member that you like to remove
![](https://d2duuy9yo5pldo.cloudfront.net/wgames/dce9cb7c-8551-4ec0-a777-45e727cc0f52-2t.png)
Click "Make Co-Leader"