Ok, I will show you in this tutorial an easy and freeware software to use to make transparent gif images. You can also make .png and many other transparent images with this software.
In this tutorial i am using The GIMP to transparent images. GIMP is a freeware software. In this example i am using a .PNG file, transparent and save this to .GIF file.
1. Run GIMP
2. Select file and open the file you want to convert.
3. Click on Select->By Color and then just click on the white area. You will see image like shown under. Selected area.
4. Click on Layer->Transparency->Color To Alpha. See the picture under.
5. Click on OK. And then Select File and Save As. Type in test.gif and save the file.
Thats all, now you can use this file in any kind of other background.