Welcome to the zoo.
First, the photo file has to be hosted on line some where, not on your computer. Some use Photobucket or photostash, I upload photos to my Facebook account; it's free and seems unlimited for space. Next you go to the photo file itself, not the photo app or the album, put the actual photo on screen. Right clik on the photo and choose Properties. One of the catagories in the property sheet will say Address (URL), with something like '
http://a7.sphotos.ak.fbcdn.net/h?photos-aksnc4/35954_414684394093_?767649093_4770151_4937398_n.jpg' behind it. Hi-lite that address and save, or press CTRL and c at the same time to load the address in your clipboard. In Windows 7 choose 'copy url'. For the chat, click on the Typing box. Below that are several buttons, one is Image, clik that and it puts a [img]/img] in the typing box with the cursor in the right place (between the ] and [ brackets). Press CTRL and v and the address is copied into that spot, press Enter. Simple.
The far left icon in the lower row of icons above the typing box for making a post will do the same thing here.
Sorry, I don't have an iPad and can't help there.
Fred.