Alright...now that your pics are on the website...do the following.
1. Open up the webpage as if you are going to view the pictures.
2. Get the full size picture you want to put on this website.
3. Right click the picture, and scroll down to "Properties"
4. There will be a location of the picture: like..
http://www.mypicgallery.com/car/picture1.html <--something like that, whatever you named the picture.
5. Copy that text by highlighting it and hitting CTRL + C
6. Go to this website, and when you are forming a message, where it "Img" right below the Subject line...click that, and you will notice that

should appear after your text.
That should do it, good luck!