To Deactivate a Topic you click on the Topic's name at the top of the screen. Once the drop-down menu opens, click "Manage My Topics". Once the Topic management screen opens, click the Deactivate button next to whichever Topic you plan on Deactivating. When you Deactivate a Topic, the Topic will now be a part of the "Deactivated Topics" section of the Topic Management screen. 

Once you deactivate a Topic, it will no longer appear on the UpContent Topic screen. 

If you permanently want to delete a Topic, scroll down on the screen to where your Deactivated Topics are and click the Delete button next to the Topic you would like to Delete.