In HII, the left side is for identifying the device ID for a particular piece of hardware in a particular OS (e.g. Dell Optiplex 3020 running Windows 7). The Device ID will be listed at the bottom when you select a specific device (see picture below).
After you select a device you need a driver assigned to, you can search for drivers on the right. Normally I like to search based on the Device ID. Your search results will populate down the right side of the screen based on what you have loaded into your HII Library.
The last step is to select the driver you want assigned to the device from the right column, then click "Assign." It will show the file you assign in the "Assigned Driver" field in the bottom left.
You can also refer to http://community.landesk.com/support/docs/DOC-29230 for more info on managing your HII drivers.