Insert a table. Go to the Property Inspector and change the border value and the border colour to whatever you want. This will give all cells a border.
If you only want to give one cell a border, for example, follow the above example and make the border colour the same as the background colour. Then go to the cell you want a border on and change the border colour to the colour you want.
It is straight forward as Stever suggests, the default is no border, however watch DW for putting in a no border="0", if you change your mind after putting in a cell width for the border, as the code will not validate.
btw, worth getting the books for the version of dreamweaver and giving them a quick once over, covers the basics, if this is not possible, the lessons (tutorials) in HELP, cover a reasonable amount of the basics.
For a beginner, there's nothing finer than The Missing Manual. Once you finish with that, keep it for reference, but buy The Dreamweaver Bible. Excellent reference of a ton of stuff. I can't recommend it enough.
But don't forget to hand code. There are times when it's easier to just go in and hand code it, because DW has a hard time with certain things here and there.