1. Enable Canonical Partners Repository:
The partner repository offer access to proprietary and closed-source software and are not enabled by default.
To enable it, launch Software & Updates from the Unity Dash, go to Other Software tab. Check the first two boxes which say “Canonical Partners” and “Canonical Partners(Source Code)”.
If for some reason, you don’t see them in the list, click Add button and add below lines one by one:
deb http://archive.canonical.com/ubuntu vivid partner
deb-src http://archive.canonical.com/ubuntu vivid partner
2. Install Skype
If you have Synaptic Package Manager installed (available in Software
Center), you’re now able to search for and install skype after clicking
reload in Synaptic.
If not, press Ctrl+Alt+T on keyboard to open terminal. When it opens, run the commands below one by one to refresh system cache and install skype.
If not, press Ctrl+Alt+T on keyboard to open terminal. When it opens, run the commands below one by one to refresh system cache and install skype.
#sudo apt-get update
#sudo apt-get install skype skype-bin
Once installed, launch Skype from the Dash/Menu and enjoy!
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http://tipsonubuntu.com/2015/03/24/install-skype-4-3-in-ubuntu-15-04/