There is currently no method to change the installation location for

It is set to install itself on your main drive (Typically C:/) under Program Files (x86)/Raptr Inc/PlaysTV. 

Generally the client by itself does not take much space; however if you want to keep recorded videos off of your main drive, you can change the location recorded videos are stored. Just go to the Preferences under 'Advanced' and find the Header: Folders