With Synaptic Package Manager:Open the Software Sources Window:
- Synaptic Package Manager: Settings -> Repositories.
Make sure you have universe, multiverse and restricted sources checked in the first tab.
Click on tab Third Party. Click on the Add button and enter your chosen repository (for me the next line):
deb http://giss.tv/~vale/ubuntu64 ./
(for AMD64 (and also Core Duo Intel64), by Valentina Messeri)
Clicking Add Source will display the new repository enabled in the Software Sources window.
You should now see Cinelerra in the list of packages available in Synaptic.
Follow Synaptic instructions for installation.