To delete a file in CM Manager, go to your CM Admin tab and choose CM File Manager.

Expand your "Portal Root" folder to view all the folders on the server.

Find the folder that has the file or image you want to delete. Click on it and the contents of the folder will display to the right. Find the file you want to delete and click the box to the right of it to select it. Then click the red X to delete the file.

You may get a pop up window asking you to confirm the deletion. Click "yes" to delete.