If your own lens or camera is not part of the database please check http://wilson.bronger.org/lensfun_coverage.html for a daily updated list covering the status of the current development version. Maybe it is already there and your local lensfun database is out of date.
If your camera or lens is even missing in the development version please request an entry for your camera in the Support Ticket Tracker. For new lenses, the preferred way is to upload RAW images at Lensfun's calibration service. Lensfun's database maintainer then creates a lens profile, includes it into the database, and sends a copy to you.
Alternatively, you can do the calibration yourself. Below is a list of several tutorials that can be used as an introduction. Which method you choose depends on your experience and on the effort you want to spend.
Lens calibration tutorials: