DutchBarn

I am adding shed roofs over decks on two sides. One side of the roof would be against an end wall. The other shed roof would be against the main roof. The shed roofs will be a 3/12 pitch and the main roof is a 8/12 pitch. I am able to manually draw the roofs, but I cannot get them to combine into a wrap around roof. In addition, combining the main roof to the shed roof as well. Are there videos on written instructions that would help create these roofs?