Eric,
I don't know if that was my download or Robert's, I don't remember posting one in the gallery. But anyway to answer your questions:
Normally when you download the source code there is a compiled folder, and uncompiled. Depending on how the file structure was built in the zipped code will dictate how you need to go about unzipping.
If you are just using the viewer you would move the images in the zipped assets folder, and past them in your in your assets folder, and then the <xxxx>Widget.xml and <xxxx>.Widget.swf into a new <xxxx> folder under widgets. I would do this with your file explorer.
I am assuming you are using FB to do some other coding, but you don't have to to add custom widgets to the Flex Viewer, as long as you have compile code (xml, and swf).
Now if you are using Flash Builder to recompile the widget then it is a little more complicated, but not impossible (I am still a beginner too). You want to copy files out of the uncompiled zipped folder.
Again copy the images out of the zipped assets folder and paste them into the assets/images folder in the source folder (src). Then unzip the a full zipped code folder for the <xxxx> widget and paste in to the Widgets folder. When you open your new folder under the Widgets folder you should see the xml, and mxml. if you leave the assets in the same folder it is ok, you'll just have to reference that in your config file. Attached is the structure you would have in FB. You don't have to put anything in the com folder, just assets and widgets, unless you start programming the API itself. You have one more step to compile the widget now. You will have your open project click on project > properties. It will open the properties dialog. On the levt side of the screen select Flex Modules, then click add and browse to the new widget folder and the mxml file for that widget. I have attached a picture of what that looks like too. Add the widget to the config file (the one under the src file) and run, it will recompile the widget and place everything in the bin-debug folder compiled. Hope that helps.....
[ATTACH=CONFIG]11541[/ATTACH][ATTACH=CONFIG]11542[/ATTACH]