You may switch accounts by signing out of your current account, and then logging back in with the account of your choice.
To log out on the web, click on the icon to the upper right of the page. The sign out button should be at the bottom of the drop down menu.
For iOS/Android versions of Cluster, to log out, select the icon to the upper left of the page, choose “Settings and Privacy”, and the sign out button should be at the bottom.