Hi @heathersbender,
You should just be able to give them the link to your canvas instance (blah.instructure.com), and that should allow them to login with whatever password they created when you invited them, assuming you invited them via email address and the accounts were self-created. If an admin made the user accounts in your Canvas instance, you'd probably need to talk to that person to find out how they'd prefer the users to get in your course again. There are quite a few variables at play here, so I've given my best guess as to your scenario, but if this advice seems totally incorrect, let us know and perhaps we could investigate alternatives.
You could also contact Canvas support about this if that's an available option for you. They'd be able to provide more accurate info as they'll see your exact Canvas instance and settings, which members of the global Canvas community here cannot do.
-Chris