Use a url img tag
In the post reply screen, wher you type your responses, you wil see a bunch of url hypertext stuff. I don't really understand it either but if you click img then enter the location of your photo, then click img again (those are called tags) your pic will display automatically when the post opens.
Example...using a link you posted earlier
[ i m g ] http://www.aquaticplantcentral.com/forum/album_pic.php?pic_id=738
[ / i m g ]
I added spaces between the letters of the tag so that it would show what is done and not show the pic. Remember to use  these and the one at the end gets / a backslash.
Similarly, if you wanted to make a clickable link
do this...(once again I will add spaces so it does not work)
[ u r l = http://www.aquaticplantcentral.com/forum/album_pic.php?pic_id=738
] link [ / u r l ]
Basically, what ever is in between the tags shows and what is in the tags is the command. If you hover your mouse over the buttons at the top for the tas, it shows the varoius ways of typing them in manually and also the short cuts (ie alt=h ) The nice thing about using tags and hyperlink stuff is that it makes your posts look cleaner. You pics just have to already be on the web. You can upload them to your personal photo album at APC and link right ot that
Hoped that helped