It's quite easy to create tooltips, if I'm thinking of the same thing as you are, lamunu. I'm assuming you mean that when someone hovers their mouse over an image a little "text tip" will appear describing that image. To that you would use the ALT tag. As you're using Dreamweaver you can view the HTML content of your page in the Code view. Insert your image using the:
That will place the image on screen. To add the tooltip, use the ALT tag like this.
<IMG SRC="your_image.gif" ALT="This is my image">
Now when someone hovers their mouse over "your_image" the text "This is my image" will pop up, like a little "tooltip".
I hope that's what you meant, lamunu.