Disclaimer: your experience may vary. Some neighborhoods have reported that they're directed to a miniprogram for the sign-up process.
Step 1: Find Out Where To Register
Some have said there'll be a sign posted up in your neighborhood letting you know where your nearest registration center is. Look for "kouzhao / 口罩".
I didn't have one in my compound, although looking around, I did find a letter announcing that a neighbor two doors down was in arrears and would have his property auctioned off in a week, so I've marked that down in the old calendar.
I asked our compound bao'an where I could register—or rather I pointed to his face mask and he seemed to understand—and he told me it was in another compound about a block away from mine.
Once there, I pointed to another guard's facemask and he walked me down an alley to a table in a courtyard with some helpful ladies.
Step 2: Register
You will need your passport and either a rental contract with your name on it or a temporary registration permit. I showed the electronic version of my temporary registration permit (which I got by registering with the police online) and that seemed to work fine. The helpful, hard-working ladies at my registration center spoke English, but as long as you have your documents out, nary a word in Chinese need be spoken.
They'll check your household off a list, ask for a contact phone number, and give you a sheet of paper with an address where you can get your mask ration.
Optional Step: Pose For Photos
If you feel like it. They seemed pretty stoked a foreigner was going through the procedure. Help the hard-working public servants get a little kudos from their supervisor.
Step 3: Wait For The Call
They'll call you. Each neighborhood committee is given its daily quota by the pharmacy and they work down the list first-come-first-serve. The hand-out period is between 9am-6pm.
My designated pharmacy is Leiyunshang, which is cool because it's famous, and also bad because it's famous for having huge lines. So I didn't get a call by 6pm day-of, or even the day after, even though I had registered around noon. When I got in touch with the helpful registration ladies, they said I might have to wait up to a week.
Logistics for a city of 25 million is super hard even when it isn't on lockdown.
So, while I'm just sitting here, let's shift perspective to my friend who...
Step 4: Got The Call
The phone call will be in Chinese, but basically translates to "hey you can come get your masks now."
Step 5: Go Get Your Masks
Show up. Show your paper. Get your masks. They cost 2.30rmb for a pack of five.
Unfortunately they're ho-hum surgical masks rather than stylish N95 masks, so they won't do much except block the rest of the world sneezing or coughing directly into your mouth, or, just as important, block you from sneezing and coughing on the rest of the world.
Still. Face masks! Better some than none.
That's five masks per household, not per person, and five per allotment. The first allotment is from February 2-11.
Can't find your neighborhood committee? Call the multilingual city helpline 962288, give them your address and they can point you to it.