The file explains how to update the application icon from the source 
qtenki icon qtenki_icon.svg.

Using inkscape, I export the icon in png format in the following sizes:

16x16, 32x32, 48x48 and 256x256.

Then, using gimp, I create a multi-layer image with one icon size
per layer (from the above exported files) and save as .ico. I only
applied PNG compression to the 256x256 version.