Changing the theme photo to your own image

In trying to figure out how to get started with my web site by changing the theme photo to my own image, I read through the forum and what I found seems to suggest that the only way to do that is to use something you’ve uploaded on an FTP service through your web host. Tell me it ain’t so! Why can’t you just use an image through the library?

I’m (obviously) a newbie here, but I can’t find any good guides to help me to start from square one. E.g. just figuring out how to organize pages is confusing. I want to have a “home” page, but when I create that it then gives me two, the actual main page that is my site and a second one I’ve named home. This is just an example to let you know how clueless I am in the hopes that you can point me to somewhere that will begin with basics as basic as can be. The forum seems too advanced, wordpress for dummies is more about blogs (I’m trying to create a web site through www.remarpro.com) Thanks for any help on this.