To remove a catalog item, click the Policies link in the Navigation bar, then select the Catalog button on the top-left section of the page.

Choose the appropriate tab for the type of the item you want to modify. In this example, we will be using a Custom Software item 

Find the item you would like to remove, then click either on the icon or the name of the item. A modal window with the item details will appear. Click the Delete button on the bottom-left of the window.

Confirm the deletion, then the item will be removed from your catalog as well as from any policy that was using it.