Posting full-sized pictures?

[cookderosa]

since our members are feeling especially generous and kind, can someone explain to me (in the simplest language possible) how I get a picture to have a url? So, let's say I take a really cute pic of my cat, and want to post it here (don't worry- i won't) I can't do that because it's in my computer as a file, not on a web page. So, since I don't have a website, is there some other way? Is that what the photo sites are for?
Sorry, I'm old. I only JUST stopped saying "rewind" and "fast forward."