The Nationals' May 17 game against the Pittsburgh Pirates, which was rained out, will be made up as part of a single-admission doubleheader July 2. The first game will take place at 3:35 p.m., and the second will start at 7:05 p.m. or later, depending on when the first game ends.
If you had a ticket for the May 17 game, you can exchange it for a ticket for the doubleheader at the Nationals Park box office. And if you had a ticket for the original July 2 game, your ticket will be honored for both games of the doubleheader. More ticket exchange information is available here.
Because the first game falls in FOX's national blackout window, MASN is unable to televise it. The network's Nationals broadcast that night will begin after the first game is over.