All right, so we recently bought this house. The inspector that checked it out for us before we bought it was out at the house when it was raining. He said that he noticed that there was staining on the OSB where water was leaking back on to it. He recommended that we get some drip edge sheet metal and place that over top to keep the water from continuing to run back on the OSB. He said the weight of the roofing should keep it in place.

I'm having trouble visualizing how to do this repair. There is a gutter attached to this part of the house. The drip edge sheet metal that we bought is L-shaped.

The inspector said that it appeared that this started happening when someone or something maybe nicked the tar paper, creating a little channel for the water to start getting through to the OSB.

Can anybody tell me more about what to do here? I would love step-by-step how-to instructions if anybody can provide that...

The long leg of the drip edge slips between the shingles and the roof deck above the gutter. It stops water from rolling over the edge of the shingle and wicking back againist the OSB.

http://www.rollex.com/pdf/dripedge.pdf

It really should not be "L" shaped. The drip edge is available in various "drops". It's sometimes hard to find the short "drops". The "drop", I'm referring to is the vertical distance in the picture.
Getting the wrong size, can sometimes interfere with the gutter.

What happens is that water that tries to run vertically down, gets diverted at an angle out and away.