Tristen,
You can cut the sinew out of the lower legs of a deer, both front and back legs. Also, you can get large sheets of sinew from the backstrap (located on either side of the spine). The leg sinew looks like silvery cords....you cut them out, then just hang them somewhere and let them dry. Also, keep an eye out over the next few months for my article "How to remove sinew from a deer". IT will be coming out in Primitive Archer and I think that should be much easier to follow because it has pictures showing how sinew removal is done.