If you go to the clicksmilies site......
Click on the first drop down menu---the one that says smilie categories.
Pick a category and the different smilies will show up on the right hand side of the screen. It may take a second for all of them to load.
Find the one you like and click on it. At the bottom of the right hand side a white bar will show the code for that smilie. All you have to do is highlight the entire code, copy it, and then paste it on your message.
The second pull down is for the smilies submitted by others. If you get bored with the main ones try the second set.
Oh and as long as the code starts with (img) and ends with it you wont have to use the add image box on the reply section. The ones at click smilies already have the image tages so you can just copy and paste directly to your message.