Step 3 - Choosing an instruction Since the user starts with a clear project, the source list on the center of the main window is empty. To enter the first instruction, you should just click on the first position in the grid with the right mouse button: a pop-up menu will appear, showing all instruction supported by Quexal outlined by functional groups.  The first instruction in this project will load the data of the first source image into the SourceImage1 variable, so you should add a Move 64 bits instruction.  The most frequently used MMX instructions also appear in the toolbar, so you can click on the 64 button too: as soon as you learn what those symbols mean, you will be able to enter the source code in no time. A less user-friendly but even faster way to enter instructions is the usage of accelerator keys.