To Import an Icon from a Bitmap File

In the Customize dialog ( File > Settings > Configuration > Customize ) click the Icons tab.
Click the arrow on the Import Icons icon and select From Bitmaps.
The Import BMP dialog opens.
From the Generate drop-down menu, select the icon sizes that you want to import.
Note: You can select a specific icon size to import (16 x 16, 24 x 24, or 32 x 32) or you can select All Icon Sizes, which imports the icon and scales it to each of the three sizes.

Note: If you choose a specific icon size to import, you can use multiple Bitmap images to represent one custom icon.
Click the browse icon.
The Select Image File dialog opens.
Navigate to the BMP file that you want to use and click Open.
Click OK.