When you’re finished editing your movie in iMovie, go to the "File" menu and navigate to "Export Movie" or "Share".


You will now be given the option of choosing your export option. Choose the "To QuickTime" from the Export menu. As mentioned earlier QuickTime is one of the most common formats on the Internet so this option is ideal.
Most people will be able to view your movie if you choose this (56k connection speed) preset. You have several choices for the formats that depend on your needs. As you are looking to put your content online you should select either 1. "Web Movie, Small" or 2. "Streaming Web Movie, Small".

In iMovie, if you want to make your file ready for streaming, you can. Choose expert settings, but only if you know what you’re doing! After practice and experience you will become familiar enough with the standard options and their outcomes and want to start trying your own settings.
Click Share/Export if you chose a preset format. Give your movie a filename, choose a folder in which to save it, make sure you call it something easy to remember and store it where you can find it. Click "Save" to save your movie to a file and finish the export process.

The time to export depends on the compression settings and the power of your computer.