I have set up user accounts? How do the users log into our account?

If you are referring to sub-user accounts:

https://www.jotform.com/help/232-How-to-share-forms-with-a-sub-account-user

They should receive an invitation email with a link to sign up for a JotForm account if they do not already have one.  If they already have one, a shared folder will be created in their account containing the forms that have been shared.