Click on the Tool Tip icon in the top of the Serato DJ main screen to enable Tool Tips. This is located in between the MIDI and setup button in the top right hand corner of the screen. Tool Tips provide a handy way to learn the various features of Serato DJ.
Move the mouse over a section of the screen to bring up a context sensitive tool tip. Holding the mouse over the Tool tip button with Tool Tips turned on will show you a list of all keyboard shortcuts.
For more information about how to use Serato DJ, download the Serato DJ Software Manual here. For more information on your Serato supported hardware, please refer to the hardware's manual from the manufacturers website.