What version of Skype do I use for Mac 10.7.5? And where do I get it?
You need Skype 6.15 to be able to install it on Mac OS X 10.7.5. Luckily, the developers provided a page with information and the downloads necessary for that version of OS X.
You can use the direct download URL: http://download.skype.com/macosx/Skype_22.214.171.1245.dmg
Browse the page with the information: https://support.skype.com/en/faq/FA34498/which-version-of-skype-for-mac-os-x-do-i-need