Well, it depends where you have them stored. If you have them on your computer, you can upload them through attached files. When you wanna post, you see a section called "manage attachments" in the additional options. Just follow what is said. You browse your computer, upload the pics and they appear!!
But if they're too big, you have to resize them first.
If you have them on the net, in some online photoalbum, or on some sites, just give the link to them and put it into the code [IMG]link[/IMG].
Hope I've helped.