Fundy Album Builder and Workflow install the same way. Please follow these instructions regardless of program.
Double click on the install package and open with your default archiving software. (Album Builder pictured here, but it will say Work Flow)
Once you have extracted the folder, open it. (Album Builder pictured here, but it will say Work Flow)
Find the folder labeled CS5 installer and open it.
Double Click the .zxp extension to open Adobe Extensions Manager. (Album Builder pictured here, but it will say Work Flow)
Click "Accept" and extensions manager will install the file into your extensions. If you had a previous version of Album Builder, It will prompt you to overwrite the file.
Open Photoshop, and navigate to Window>Extensions. Verify that Work Flow is installed.