Well, one method is to plug the phone into your computer and copy the pictures over. Then use a photohosting service like photobucket, imgur, tinypic, or whatever else. Then copy the image url and past it here inside [img*] and [/img*], but without the *.
Or, some photohosting services support uploading directly from your phone. Sometimes they will give you the image url in text to copy, but more likely than not you will have to click and hold on the image. A prompt will appear, allowing you to copy the image. Sometime this gives you the image location to paste directly into a forum post, but sometimes you need to paste it into something like the google search bar, then select that text and copy it. I have no idea why that happens, but that's how I have to do it.
Some hosts, like instagram, don't allow you to click and hold on an image to get the image url, at least not when using the App. Instead that gives you a "share" link that leads people back to instagram. Like this
http://instagram.com/p/ifRAIuL9VN/
I use my iphone almost exclusively on here, and you can do everything you could on a pc, it just takes some different tricks.