Are you referring to the "Buuf" download file? I personally found that to be an extremely unorganized file when I downloaded it, but if you can understand it, that's all that matters. Anyway, on to the explanation.
Step 1: Move the icons you want on to your SD card in a file you can easily set apart from the others.
Step 2: Download an app that allows you to create icons. I personally use FolderOrganizer Lite.
Step 3: (My instructions limited to FolderOrganizer Lite) Launch the app and press the tab "Apps" located at the top. Locate the application you want to create a custom icon for. Press the drop down arrow to the right of that app, and then press the Icon button in that drop out bar. Since you are not using an official Icon Pack, choose Android Image Gallery. Select the picture set on the SD card that your images are located on, and then the specific image you want for your selected application.
Step 4: Rinse and repeat for each of your other apps you want a custom icon for.
Step 5: To apply it to your dock/homescreen, press Menu, Add to Home, Widget, FolderOrganizer item, Apps, and your desired app.
Note: Keep in mind these icons you want are 1080p resolution/size icons. If you want a lower resolution or size, you're going to have to use Microsoft Office Picture Manager or something to edit them. I would search the Market for Icon Packs and see if you find any you like there, as they are optimized for most devices already.