You can manually place tags on your devices from the Devices table. You can access this table from the upper right-hand corner of your GUI.
From the Devices table you will place, or remove, your tags by clicking in the Tags column.
You can add as many tags as you would like to a particular device by clicking the Add button along the bottom of the small pop-up window. From this same window, you are able to set the expiration time, as well as delete a particular tag.