iPhoto Library Manager > Help > Opening a library
Opening a library
iPhoto Library Manager lets you manage multiple iPhoto libraries, but only one of your libraries can be open in iPhoto at any given time. In your list of libraries, whichever library has the button to the left of its name selected (i.e. colored in blue) is the currently active iPhoto library. Opening iPhoto, either by using the "Launch iPhoto" button in iPhoto Library Manager, or by clicking on iPhoto in the Finder or on the dock, will display that library in iPhoto.
To switch to another library, click the button next to that library in iPhoto Library Manager to make it the active iPhoto library, then click the "Launch iPhoto" button (or "Relaunch iPhoto", if iPhoto is already open) to see that library's contents in iPhoto. You can also just double click a library's name in the list to open the library.
iPhoto Library Manager's icon in the dock provides another way to switch libraries. Either control-click its dock icon, or click and hold on the dock icon, and a menu will come up showing you your list of libraries. Select one of the libraries from the menu, and iPhoto Library Manager will open up that library in iPhoto. Note that iPhoto Library Manager must already be running for the dock menu to appear when you do this. If you want to keep iPhoto Library Manager running, but without its window cluttering up your screen, uncheck the "Quit iPhoto Library Manager after closing the main window" checkbox in the preferences window.
If you have iPhoto '09 or later, you can also simply double click the library itself in the Finder to open that library up in iPhoto. Be aware though that this does not work with iPhoto '08 - double clicking the library will not open the library you clicked, instead it will just open whichever library was last opened in iPhoto. This can be confusing, since you can double click one library but end up seeing another library's contents.