Any user of Metanet's N user level database NUMA will know how clunky the interface is for copying user created levels to your copy of the game. NumADD, eradicates the need for copy and pasting and makes transferring levels the work of one mouseclick.
Open your Firefox browser and follow this path: Tools>Add Ons>Get Extensions
You arrive at the Firefox Add On Homepage. In the search bar type "numADD" and hit return. Your search should only unearth one result: numADD by coolguy5678.
Click "Add to Firefox" to the right of the page and install the Add On(Firefox requires you restart to complete installation).