You need to water the entire bed thoroughly, and then apply a thick layer of mulch over the soil. Cover all the soil except where you planted your seeds. Seedlings are pretty tough, and can probably break through that crust, especially if you keep the surface moist ... unless you planted too deeply. You may need to lightly water the exposed soil more than once a day.
If you don't know what to use as a mulch, just type the word into the search box at the top of the page. You'll find a lot of discussions on the topic.