How to Make a Icon with a Image
You will need to download
IcoX portable it is portable no need for installation IcoFX Portable | PortableApps.com - Portable software for USB, portable and cloud drives
Gimp needs installed GIMP - Windows installers
The icon I am going to make has 13 layers those layers are 48 x 48, 32 x 32, 24 x 24, 16 x 16, 48 x 48, 32 x 32, 24 x 24, 16 x 16, 256 x 256, 48 x 48, 32 x 32, 24 x 24, 16 x 16,
The biggest image is 256 x 256 so that will be the size of the starting image.
I am working with a 256x256 pixel image in .png format.
OK lets make a eye.icon
Either drag your image to the workspace or click Open and navigate to your image.
The New Image box will open make sure True Color + Alpha Channel is checked then check 256x256 and then Click OK.
Your first image should be loaded Right Click on the 256x256 at the top and then Click on New Image.
Repeat step #3 above for each of the different sizes in this case I am doing 48 x 48, 32 x 32, 24 x 24, 16 x 16.
You should have five images ranging from 256 x 256 down to 16 x 16 now Click on File. Click on Save As. Give it a name and Click on Save.
Now we to make a four image ranging from 48 x 48 to 16 x 16 Right click on the top 256 x 256 image and Click on Delete Image. The Confirm box will open Click on Yes.
Now we want to save the four images Click on File then
Click on Save As. Give it a name different than the first one then Click on Save.
Open up Gimp either drag the first set of five images that you saved into the workspace or Click on File and click on open and navigate to your image.
You will see the five images in the layers box Click on the top layer and then dragged the second image with four layers onto the workspace it should be on top of the five images Click on the top layer again and drag that second in the with four layers into the workspace again you should have 13 layers.
Now we are going to save the icon Click on File then Click on Save As. Give it a name with the .ico then Click on Save. The Save as Windows Icon box will open
you should see 13 different layers when Click on Save.
You should have a 13 layer icon, not all icons are built the same I have seen icons with as little as one layer and as many as 24 layers so you will have to study how the icon was built.