A good friend in Louisiana went to renew ACA coverage and was told (by the site) he was put on Medicaid when he entered his income figures (which are low). He left it at that assuming he was now enrolled in Medicaid, but can it really be as simple as that? Should he now receive a MediCaid card or account number or some such? What should he do next? I am worried about this, and grateful for any help you can provide.
HealthCare.Gov (or your state marketplace) can enroll you in Medicaid if you qualify and you give them the necessarily information. You can also enroll directly with your state Medicaid agency.
To check that you are enrolled in Medicaid and approved you can contact your state Medicaid office and follow up (you can also call the marketplace and confirm that everything went as expected). Learn about getting Medicaid and CHIP from HealthCare.Gov.
To be clear then, it is likely it really was that simple for your friend. With Medicaid you can apply through HealthCare.Gov during open enrollment, and they will coordinate with the state Medicaid office for you, or you can apply directly through your state's Medicaid department. If you are uncertain, simply call and follow up.
TIP: Although it should be taken care of, make sure the old plan is cancelled for next year (this could happen if last year's coverage was set to auto-renew).