How to contribute to pdfbox

[zhoulei]

Hi
   I found pdfbox at Github,and then I am using it for creating pdf. 
And i wonder how can i contribute to pdfbox, tips at Github has no enough 
infomation for me. 
   I checked the pdfbox project at github, i found it is a mirro, 
could you please tell me if you will check       the issues 
at github. And if you will accpet pull request at github.
   think you.