If you have a library on one computer that you'd like to transfer to another computer, the process is pretty straightforward. All the library's data is contained in its library folder, so all you need to do is copy that folder from one computer to another. This can be done either by using target disk mode, or by copying the library to an external drive first, then attaching the external drive to the other computer and copying it to that computer's internal drive. Once the library is on the destination computer, simply add the library folder to iPhoto Library Manager, and you can start using it. Keep in mind that the destination computer should have a version of iPhoto that's equal to or newer than the version installed on the computer the library is coming from.

See also:

Adding a library

Storing a library on an external drive