If your camera/lens combination is not already supported there are ways to create your own database entries and/or to support the project by providing RAW images. You find more information and tutorials at Lensfun.
The documentation can be found at lensfun: Lensfun: A library for rectifying and simulating photographic lens distortions, it contains a chapter about the file format of the database and a description how to add own entries (chapter “Filling the database”).