When MegaDrum starts it first shows a copyright info for a couple of seconds:
<MegaDrum.info > <(c)D.Skachkov >
and after that switches into a "VU meters" mode and shows two rows of 16 blocks:
The top left block shows HiHat pedal position. The bottom left block shows Kick activity. The rest of the top blocks show hit levels on Head/Bow channels. The rest of the bottom blocks show hit levels on Rim/Edge channels. If you set 'Big VU Meter' to Yes then the whole top raw of blocks will show HiHat pedal position and the whole bottom raw will show hit levels from all channels.
Press any key to enter the Menu. After you entered the Menu you can navigate between settings with keys LEFT/RIGHT. Once you navigated to a desired setting you can change it by pressing keys UP/DOWN.
First two screens of Menu are informational rather configurations settings. The first shows copyright info and the second shows Firmware version and the Atmega's crystal frequency, e.g. "20110417 20MHz". While on the first screen you can change LCD contrast by pressing UP/DOWN.
MegaDrum autmatically exits the Menu after 10 seconds of inactivity. You can force MegaDrum to quit the Menu by quickly pressing and releasing the HiHat pedal.
If your MegaDrum also has rotary encoders, you can use them to navigate or change config values. The left encoder is used for navigating the menu and the right encoder is used for changing config values. You can also use a "single encoder" operation mode if your left encoder has a built-in LEFT key (button). In the "single encoder" operation mode the left encoder can be used both for navigating the menu and changing config values. The "single encoder" operation mode is enabled/disabled by pressing keys LEFT and RIGHT simultaneously. When the "single encoder" operation mode is disabled (default) the menu shows standard "filled up/down arrows" in the bottom rightmost LCD character block. When the "single encoder" operation mode is enabled the menu shows "empty left/right arrows" if the encoder is in the LEFT/RIGHT mode or "empty UP/DOWN arrows" if the encoder is in the UP/DOWN mode. When the "single encoder" operation mode is enabled, switching between LEFT/RIGHT and UP/DOWN modes is toggled by pressing the left encoder's built-in button.