Below are steps to Install Skype for Linux in Ubuntu System.

Step 1: 

Go to Terminal

Step 2: 

Uninstall Skype (If you already have OLD Skype):

sudo apt-get --purge remove skype

Step 3:

Go to https://www.skype.com/en/get-skype/ and download Deb package (skypeforlinux-64.deb)

Step 4:

Now install using below command

sudo gdebi skypeforlinux-64.deb