You're obviously doing something wrong.
Spoiler: Simple Tutorial for Blake (click to see content)
1. Open Mugen.
(http://i.imgur.com/IFTqC.png)
2. Start a match (In any mode)
(http://i.imgur.com/Xr9Bi.png)
3. Press the Ctrl button and the letter D at the same time.
(http://i.imgur.com/FyEIU.png)
4. Pressing these buttons will trigger the debug info (located in the upper left and bottom left hand corner of Mugen).
(http://i.imgur.com/dygHP.png)
5. Once you see the debug info, press F12 to take a screenshot.
(http://i.imgur.com/b4i0P.gif)
6. Once saved, upload your screenshot here (http://imgur.com/).
7. Once uploaded you will see codes to your right. Copy this code and paste it here on this thread to post your screenshot on this thread.
(http://i.imgur.com/wfwaJ.png)