First you take the picture you have on your computer, than you upload it using an image upload side. There are several, like photobucket and imageshack. I use tinypic, which you don't need an account for.

Then, you take the URL of the picture, and put it between this. [img]Link Here[/img] , and post it! Hope that helped =)

Ok, let's take your avatar as an example. You uploaded it right? You can also upload it the same way on a site for image uploading like tinypic.com. Then you take the image url and paste it between [img][/img]

See, I take your avatar is opened the image in another tab by right clicking on it and clicking open in another tab. Then I took the url of it, and paste it between the image codes like so: [img] http://endlessforest.org/community/files/pictures2/picture-24545.jpg[/img] But it doesn't work with spaces, so just remove any spaces and you have:

Oh, here is a tutorial that will probably explain things better if you need it: Click

You're welcome!