Hi Customer (name blocked for privacy),
Dreamweaver has good tutorials to get you started with learning how to use the program. Basically there are two main views for constructing web pages. The Design view and teh Code view. You can set properties for items. To set the target attribute of the link choose this in the properties section when you create the link.
You will get a better effect though by using the Lightbox JS or Lightbox JS2. These have
good easy instructions for setting up your site with these free scripts. You simply copy and paste the lines of code into the your page and change the filenames to match your images.