Go to your ISP's homepage. You should see something in the options that says something like "My Account". Use the username and password they had you use when setting up the account to log in. You should see what all they offer under your plan then - email, web, spam filter, and so on.
FTP depends a little upon the client you choose. Most come with a 30 day trial, but there are a few free ones. I can't recall any current free ones for Windows right now. Maybe someone else can help there?
Put in the address for your webspace. You should have been able to click on this from your ISP's account page. For example, I put " myweb.cableone.net" in the FTP's host space, then my account's username and password. Other settings should be fine on default. Make sure it's set to FTP. Then you just find the file on your computer and upload it.
A better description could be provided, and probably a link with a how to with pictures, once you find a FTP client to use.
You can also use your webspace to store and link other small things - pictures, text files, your bookmarks, or you can actually make a website on it.