Because store insurance does not cover volunteers, the first step is to register on the MN Responds web site. Once done, presumably, the State of Minnesoata provides the required insurance. Unregistered volunteers put the store at risk, so please don't offer "walk-up" help.
Follow the steps in this MN Responds Registration Guide.
After registering on MN Responds, you'll receive an email message with a link to another web site where you can sign-up for shifts. Do not distribute this link, because that enables folks to bypass MN Responds, which is a pre-requisite. While creating an account on the sign-up site is an option, you can sign-up without one. You just need to supply your first name, last name, phone number, and an email address for each shift you volunteer for.
The workload at stores comes in waves. Please be paitient if there's a lull in the action, leaving you with little to do for a while. Or consider switching to a different store with more open shifts if you're the type that's just gotta be busy. Weary grocery store employees will be grateful for any help you can provide, even if it's just being on-call for a quick task.
If you have any questions or need assistance, email Andrea Orest at: email@example.com