The easiest way to build frames in DW is to use it's built in Frame Object Palette. Let's create a simple frameset using this.
Start by selecting the Frames Palette under the objects menu
You'll now see a palette showing the different designs of Framesets you can choose from. Go ahead and drag the Left and Nested Top Frame palette onto the stage.
Now, in order to work with Frames, you'll need to open two palettes: the Selection Properties palette and the Frames Palette which looks like this:
Go ahead and click on one of the displayed frames and watch how the Selection Properties palette changes.
This is where you give you frame a name (remember, NO SPACES), and set things such as scroll, resize, border color, and margins.
Go ahead and click on the thicker bar which runs vertically on the frames palette.
This allows you to adjust the nested frameset with the two rows of frames.
Click on the border and you'll see the master frames.