Your CSEA member number is printed on the membership card that is mailed to you each year. It is also printed next to your name and address on the back of Focus Magazine. If you don't have access to either of these things, you can call your CSEA Field Office of Member Benefits to ask for it.
Please note: If you have lost your membership card, you can print a new one after you log in to csea.com. Just go to the "My CSEA" page.