Latest version – problem installing

Hello, I am wondering how I upgrade my blog to the latest version of wordpress. It is currently version 1.2 in a subfolder of my website, annoushka-jewellery.com. Our current platform the site runs off is BT Fresca who carry out most backend work. Would this be a job for BT fresca’s dev team or is it something we as people with admin and login access to the blog can undertake ourselves? I would appreciate if anyone could tell us how we then do this if indeed we can do it ourselves. Thank you!