I personally like to use Photobucket (though I have not tried the others)... But Photobucket is easy to use.
You go to the site:
http://photobucket.com/Get an account ((it is free)). Just click the big red rectangular button that says "Register Now".
When you are logged in you will see a box that has a clear heading on it that says 'Upload Images & Videos'... and within that box is a button that says "Browse". Click "Browse" ... and select the file you wish to upload.
Then after you have chosen the image and hit ok... Hit the "Upload" button that is slightly bellow the "Browse" button.
And there you go. You image will be on the site for you to use.
Once it is uploaded onto Photobucket you can use the IMG code ((all you need to do is copy and paste the code)) to share your images or even give the URL code ((You will see three code things once your image is uploaded: Url, Tag, Img. I tend to use the IMG code more just because then people don't have to click a link to see it. But that said... for larger images that may stretch pages I use the URL code... giving a link so that is will open a new window to display the image.))
I hope that helps. If you have any trouble with Photobucket... or even if you have any questions... feel free to PM me, I would be more than happy to help.
Have a great day and be sure to SMILE!! =^_^=!!