Not only would you need to find a download of the Liquid 7.2 installer, but if you have a modern video card, you will also need the DX10 patch.
I would suggest to either do a Google search (you never know what you will find!), or switch to a more modern NLE such as Edius (very similar workflow to Liquid's) or even Pinnacle Studio 18 (it started out as the replacement for Liquid, which we here on the forum called "NexGen") .
Good luck 