If you want to display all images on one and the same voting page, then you need to take an image manipulation program (ie paint, photoshop, corel draw, gimp, ...) and put them all into one file, then upload it to the system. There is no other way to display multiple pictures on one voting page. If you check my gallery, you will see some of these pre-combined pictures of my minis where multiple shots are in one single image.
The URL (uniform resource locator) is the text you see in your browser which starts with "http://" or "ft://" or whatever. The whole thing, not just parts of it! Its the technical term for what is also sloppily called "web-address" or "link". For example, if you have uploaded a picture on any own website (own web-space, on photobucket, on imageshack or whatever), the system allows you to link this picture instead of uploading it again (which won't be required anyway, since it would already be online, just somewhere else) by entering the URL of the already uploaded image.