The DeviceAtlas web site does not offer a form or page to add new headers to map to devices.
The best way to add a new header to DeviceAtlas is to take the device and visit the testsuite TA-DA. Logging in and taking a the tests (should take about 10 minutes) not only will add the headers to the DeviceAtlas database, but will also enrich the device profile.
If you run a site with a high traffic and do not have access to all the devices that visit your site, but you want to help DeviceAtlas improve, you might want to install and run the LogAnalyser. The LogAnalyser is a small Java and PHP application that you run on your server feeding it with the headers you have collected from your website and using a SOAP interface you upload unique headers to DeviceAtlas. In order to get access to it, you should contact us offline (da.tech AT mtld.mobi)or on the mobiForge forum.