If you're not the right person to set up AvaTax Update, click Invite Another Account User to give access to another person. You need to know their name and email address. They receive an email where they can set up their password and sign into AvaTax Update to complete the setup. Go ahead and log out after you send the invite.
The Invite Another Account User link is only available while you're setting up your first company in AvaTax Update. After a company is set up, add users by going to Settings > Manage Users.