You can give Shared Access to anyone you trust, even if they don't bank with us. When adding a new Shared Access user, we'll ask if they have a username with U.S. Bank. If they do, you'll enter it and if they don't, we'll create a temporary username for them. See: How do I add a Shared Access user?
If you've already sent the invitation and your Share Access user needs help, see: How do I accept a Shared Access invitation and complete enrollment?