After enabling plugin there will be two additional menu entries in Project/Tools.
Icon Creator is used to make icon from single file (all icon versions will be upscaled or downscaled) or six files in resolutions of 16x16, 32x32, 48x48, 64x64, 128x128 and 256x256.
Icon Replacer changes icon in exported Windows executable. Remember to use icon file created by Icon Creator because such icon is uncompressed and has exact required size.