upgrade to pro

Hi I am looking at upgrading to pro. Am running free at moment www.creativesigns.uk.com How do i upgrade without affecting the site. Also i previously asked if i could use pro on a number of sites and was told i can. How do i do this please? I'm new to websites and prefer to one click install from within wordpress. Is this possible over a number of sites or would i need to download pro then upload to relevant sites, which i may struggle with. Many thanks Karen