Purchase a dovetail jig set. The set will include (at minimum) a tungsten carbide steel dovetail bit, a tungsten carbide steel straight bit, guide bushings, and the dovetail template. Use the bits that come with the template. This type of set is the most simple and cost effective in most situations. It also does not require knowledge of the specific machine or large areas of the room dedicated to specialized equipment.
Set up the template. Make a block that is the same as the measurements mentioned on the package. The block (in the case of MLCS Woodworking's kit) will be 2 7/8-inches wide, 4-inches tall, and 18 inches long. If a 3-inch block is too expensive, you can glue panels together until they are about 3 inches and then shave the panel down to 2 and 7/8 inches. Make sure that you use a thin layer of glue and that the wood is clamped together tightly for 24 hours or until the package says the glue should be dry. It may take longer in moist places or places with poor air ventilation for the glue to dry.
Screw down the template onto the block so that the template teeth are parallel to the long edges of the block on the most narrow edge. The screws will fit into slots on the ends of the template. There are two round holes that you will use later. Make sure that the template you are using is the kind that matches the type of boards that you will dovetail (in this case 3/4-inch thick).
Clamp your jig to the table with the edge of the work that you are to use the router on flush against the block and the template on the inside corner where the two meet. Make sure that the work is on the side with the straight teeth and not the flared-out teeth. Center the board so that the teeth lay on the board in a symmetrical pattern.
Screw in the guide bushing (the little brass rings) onto the jig around where the dovetail bit goes in to serve as a collar to guide the router in the jig and protect the template. Insert the dovetail router bit into your router and tighten the bit in place.
Set the depth of the bit to the width of the other board that you will be joining to this one. Slowly guide the dovetail in and out of the grooves of the template. While you do this, hold the router flat against the template and allow the guide bushing to slide along the template.
Remove the piece you worked on and inspect it. If the cut is good, hold the other board against the first as you would like them to fit together. Use a pencil to outline the second board's joints using the cuts on the first board.
Place the second board on the opposite side and use the other bit. Remember that you use the angled bit with the straight-toothed side and the straight bit with the angled edge of the template. Set the depth of this bit to the width of the other board that will join to the one you are working on. There should not be any adjustment needed to the position of the template yet.
Line up the tracings that were made onto the second piece of wood with the teeth in the jig before clamping the work into the jig with the skinniest edge up where the joinery (attaching together of the two boards) is to take place. Again, guide the router in and out of the teeth with the guide bushing against the template.
Clean off the debris from your work. Test the fit between the two boards. If the fit is too tight, loosen the two screws to slide the jig. Slide the jig to the "pointy" tooth side of the template if you need to tighten the fit. Slide the jig towards the "square" toothed side of the jig to get the fit to loosen.
If you need to repeat the process more than once, turn the calibration boards to different edges. Once the jig is in the position that you need it to be in, chances are that you will not need to change the position for the next board of the same depth. Use the jig on the two boards using the same process.