You can find the option to become a "Postmate" in the main menu on the iOS app.
When you select that option, you're directed to the website where you can sign up to become a Postmate. You're asked for your email and password to get started.
You're then asked for more details like your name, device, market, and type of vehicle.
At this stage, you're asked for your driver's licence details and then your home address.
Here you have to read and accept a fleet agreement, before also accepting a background check disclosure.
More agreeing to disclosures, this time for background checks.
You have to enter your social security number to agree to the background checks and continue.
At this stage you're asked to book in for an onboarding session.
You're presented with a location and a list of available dates/times that you have to choose from before finally submitting your application.
Once your application is submitted, you're told your application is being processed and you should expect an email.
There's also a "What is Postmates?" video you can watch here.