Make sure the drive is formatted Mac OS Extended (Journaled)
1. Quit iPhoto
2. Copy the iPhoto Library from your Pictures Folder to the External Disk.
3. Hold down the option (or alt) key while launching iPhoto. From the resulting menu select 'Choose Library' and navigate to the new location. From that point on this will be the default location of your library.
4. Test the library and when you're sure all is well, trash the one on your internal HD to free up space.
To copy photos to an external drive select them in iPhoto and export to the external drive
To copy your iPhoto library to an external drive that is formatted Mac OS extended (journaled) drag it intact as a single entity to the external drive. This will not work with other drive formats.
To use the external drive for your active library after copying the iPhoto library over depress the option key and launch iPhoto and use the select library command to make it your default library
Thanks for everyones advice, I have managed to sort it with your help, the problem was that my external drive was not formatted to mac so I have used the one that is for my time machine backup.
What I was trying to do was to take photos from my daughters macbook to mine, is this the only way of doing that or is there an easier way.
Probably just the photos, we went on holiday and took my daughters macbook so that I could download photos from my iphone, that we took while we were away, just as a precaution in case the phone got damaged and we lost the photos altogether. How do I connect the machines together and use iphoto library managed? sorry to sound so stupid.
My problem is that I am now becoming so confused with iphoto itself, I am not really sure what I am doing, what with the events, photos and faces section and the album section, I suppose I could do with a complete tutorial on how to organise my photos correctly and I might see things a lot more simpler, is there any advice on what section in the apple community that might help me understand iphoto itself.