You can watch your home movies on Apple TV by exporting them from iMovie. Depending on your source material (SD or HD), the iMovie export option provides video encoding up to 1280x720, 24 fps Progressive. QuickTime 7.1.5 or later is required.
Note that files created using the "Movie to Apple TV" option will not be compatible with iPod.
Follow these steps to export your iMovie to Apple TV:
Once you completed these steps you can import your movie into iTunes so you can use it with Apple TV.
Note: If you have setup iTunes to copy files to iTunes Music folder, then you can delete your exported file. This option is located in the iTunes Preferences. Choose iTunes > Preferences and click Advanced. Click the General tab and then see if the "Copy files to iTunes Music folder when adding to library" option is selected.