First time here

I am making a website for my parents and I want to put a slideshow onto their webpage. I can get a slideshow on there. Its just whether or not I can update it when it is on the web. I.e. add new photos or take some away.

Another thing is that when i purchase a domain name can i take the website attached to it off, and put a different one on. Or when it is on there, no changes can be made?

Thanks for your help,