First, upload your button onto an online album. I use photobucket because it's free and it's the simplest for me, but there are tons of other free online albums to use.
Once that is done, you're going to need to get the HTML coding for installation. You need to go to http://www.mycoolrealm.com/sandbox/gbgen/
Enter the information they need, including the web address for the picture you uploaded.
Once everything is entered, click Preview.
If everything looks the way it should, click Reload and Get Code (or it might just say Get Code).
The HTML coding will come up. Just highlight it all and copy it.
Now, enter the HTML coding into the box that pops up and click Save.
After that, click Save Arrangement and go check it out on your blog!
There you go! That's all there is to it! See, I told you it was simple!