in theory it should be a matter of uninstalling your current version, go to the CCleaner folder in Program Files and make sure it is empty, reboot your PC (to be sure, to be sure) and double click whatever version you downloaded from the Builds page.
Thank you so much, this time it has worked but the only thing I did differently was I went on your link instead of going to the Piriform website, it has now saying 'Free' instead of 'proffesional'