You would install your shingles in the same manner as a regular roof, however, depending on the difference in pitch between the two roof surfaces I would take an added precaution in my preparation.
I suggest getting roll roofing and running the length of your roof continuous down the ridge at the point of transition between the two roof surfaces. Also, if you measure the distance up to the transition you may be able to divide equally to establish lap which will allow you to break the shingles over the transition. This may not give you the look you will be happy with, so I would "dry" fit the shingles at the ridge to see how it looks.
I suggest getting roll roofing and running the length of your roof continuous down the ridge at the point of transition between the two roof surfaces. Also, if you measure the distance up to the transition you may be able to divide equally to establish lap which will allow you to break the shingles over the transition. This may not give you the look you will be happy with, so I would "dry" fit the shingles at the ridge to see how it looks.