The government has a year to work out the details.  From the NYT:

Policy and tax analysts said that they had been wading through the law’s text and that many details about the accounts, like how they would be opened and funded, awaited clarification from the Treasury Department.

The Treasury Department and the Internal Revenue Service did not respond to emails seeking comment.

“My sense is there is still work to be done to get it up and running,” said Alex Muresianu, a senior policy analyst at the Tax Foundation, a think tank that generally favors lower taxes.

When will the accounts become available?

They are expected to become available next July.

Tom O’Saben, director of tax content and government relations at the National Association of Tax Professionals, said details of how the accounts will be opened and funded remain to be seen. “It isn’t clear,” he said.