This page shares some ideas on you can contribute:

• write announcements
• distribute announcements
• or other marketing
• ask people to write
• ask people to help review sections
• sign up and write a section
• sign up and review a section
• add missing content (write!)
• make improvements and do copyediting
• read the PDF and give feedback to sections
• participate in a writeathon

If you have any questions, go here.