1.Go to skype for linux download page and download the deb package file for ubuntu (32-bit or 64-bit).
2.Double click the downloaded .deb package file or open with ubuntu software center and click the install button.
3.Type your ubuntu password if needed and wait until the installation is complete.
4.After the successful installation,click the Dash home from unity launcher.And type skype in the search field.And click Skype to open.
