Short answer: However you want!

Longer answer:

Invite folks over. Pick a weeknight (weekends are sacred!), tell em to bring snacks, paperwork, laptops, etc. Have your wifi password ready.
When folks arrive, gab for 10 minutes. Then simmer down and work quietly for half an hour. Alarm goes off, 10 more minutes of gabbing. Rinse, repeat, till whenever you want everyone out.
Important rule: No doing your job! Resist the urge to get your paying work done. Admin Night is for admin.
In the gabbing part, share what you’ve learned: tricks for getting through that United phone maze, the email address of someone helpful at Verizon, wisdom on how HSAs work. No more navigating this stuff alone!
At the end of the night, go around the room and have each person name one thing they accomplished. Cheer! Loudly!
Schedule the next one, while you’re still high on the evening’s success. Weekly? Monthly? Bi-monthly? Just get it on the books.

Bone up in between gatherings! My hope is that Admin Night isn’t just a fun way to tackle our to-do lists. I want us to wake up to how they got so oppressive to begin with. I’ve written about it here, and folks like Donald Moynihan and Pamela Heard have written about it a ton. Share with your group. You’ve just joined the funnest, nerdiest, most productive resistance ever.