iMovie ’11 has no File>Save feature, so you’ll be doing the transfer through the Project Library. You can access this by clicking on the Project Library button on the upper left hand side of the iMovie window. From here, you can drag the project from its current place onto the hard drive or USB drive of your choice. iMovie will ask whether you want to “Copy project” or “Copy project and events.” Choose “Copy project and events.”
This will create two folders on the destination drive. A folder called iMovie Projects holds your project file and a folder called iMovie Events holds the associated footage. If you’ve added audio and photos to your movie, it’s stored within the project file. You can see this by right clicking on the project file and then selecting Show Package Contents.
Note: If you don’t see your destination drive within the project library window, this may be because your destination drive is not correctly formatted. You can use Disk Utility to reformat your drive. If you will only be using the drive on Mac, I recommend choosing the format called Mac OX Extended Journaled. If you will use this drive on Mac and Windows, I recommend choosing the format called ExFAT. Reformatting your drive will erase it, so this is usually a step people take with new/empty hard drives. If you have data on the drive you want to keep, move it to another drive before reformatting this one. After reformatting, move the data back onto this drive.
Sometimes we make mistakes or the software glitches causing photos and audio tracks to get lost in the shuffle. Always keep these assets organized in a separate folder on your drive. Should you need to rebuild your project, you will be glad not to have to re-gather these pieces. I don’t mean to scare you, but video editing in general involves a lot of time, pieces, and processing power. Lots of things can go wrong, so it’s best to be extra cautious and organized.
For additional video tips and resources, see Help! I need to make a video!