Hi, and welcome to 3FC!
The images you mentioned, the thumbs up, thumbs down, etc, those are post icons which will appear next to the thread title.
To put images in the actual post, use the smilie pad to the left side of the text area (on the reply page). You can click the "Get more" link to get a popup page with over 100 different smilies to choose from. Click them and they automatically appear in your post. You will also get used to the codes and manually type them in, too. For example, a : and a ) next to each other make
Hope this helps!