Welcome to Hubpages, Catherine1416. Lovebuglena said it well. No, you don't need your own web page first. Hubpages does it all for you.
Basically, Hubpages automatically gives your hub a unique URL (web address) for you whenever you start a new hub. The URL they give you will be based upon the title you put for your hub. So just click on "start a new Hub" and go from there... it will all work out. Hubpages handles a whole lot of things like that automatically for you, so just go with the flow....!
And as Lovebuglena said, it's possible for you to change the URL if you don't like the one they picked for you... but only when you start the new hub, you can't do this after the first screen. (Don't worry about this last bit for now if it's confusing).
Keep asking questions if you're not sure or get stuck. I have found Hubpages to be a helpful community.