You don't need a control number to enter your W-2. If you get errors when attempting to e-file with an empty box D, just enter any number in this format: 5 digits, space, 5 digits (for example, 12345 67890). The IRS doesn't care what's in box D.
If you get errors when attempting to import your W-2 with an empty box D, select Type it in myself and manually enter your W-2.