With iPhoto not running, manually rename or move your main iPhoto Library folder, then rename or move the desired iPhoto Library folder so it’s called just “iPhoto Library” and is located in your Pictures folder.
When iPhoto is not running, rename or move the iPhoto Library folder, launch iPhoto again, and when iPhoto asks you, click Find Library and locate the desired iPhoto Library folder (Figure 2.22).
Figure 2.22. After renaming or moving your current iPhoto Library folder, you can switch between iPhoto Library folders by clicking Find Library and locating your desired iPhoto Library folder.