You use the fork button on the project in github and check out the project to your desktop. Open the project in netbeans and update it.
I'm guessing it just embedded the libraries in it so you will need to update them to the latest or alternatively switch to cocoapods
https://www.codenameone.com/blog/tip-use-ios-cocoapods-dependencies-native-code.html if possible
Compile the project and test it by replacing the cn1lib in your project (don't forget refresh-libs).
Once it works submit a pull request by committing your changes to the fork and clicking submit pull request.