Start on one end of your roof. Attach the heat cable to the first row of shingles above the gutter with the manufacturer provided shingle clips.
Run the cable at an angle up to approximately the third row of shingles from the gutter. Attach to the shingles with a shingle clip. The distance between the low and high point should be approximately 1 foot if measured in a straight line along the roof.
Finish the zigzag pattern across the entire roof attaching shingle clips at each high and low point.
Run another heat cable along the entire length of the gutter and attach with the manufacturer provided gutter clips.
Slip a length of cable down each of your downspouts all the way to the bottom. This will keep them free of ice and provide an exit point for the melted water.
Plug each of the heat cables into a GFCI rated outlet. They will automatically turn on when below freezing weather is detected and then turn off when the temperature returns to above freezing levels.