The library needs to support objective-c. Then you create a binding project. See thread
https://github.com/xamarin/xamarin-macios/issues/17527
currently c# can only call objective-c entry points. to call swift, the swift code needs to support an objective-c interface or an objective-c wrapper needs to be created
https://developer.apple.com/documentation/swift/importing-swift-into-objective-c
once you have the objective-c entry point, you then create a C# wrapper for the entry point. you may also be interested in binding tools for swift: