To be able to delete an index you will have to delete all the sub indexes underneath.
From the xCenta Dashboard, click on Tools > Admin in the top right of the screen.

From the administration screen, click on Manage Site Indexes and Forms.

A new page will appear, click on the relevant index.

Delete all the forms within the sub indexes by clicking Select / Deselect All this will tick all the forms automatically, and then click Bulk Delete Forms.

Click on the icon to delete the sub indexes.

A new pop up will appear, click on Delete form.

Once you have deleted the sub indexes, click on the Indexes tab.

A new page will appear. Click on the icon to delete the index.

A new pop up will appear. Click on Delete Index.

If you are unable to follow these instructions, you may not have the required user permissions. Please contact your Site Administrator.