Spruce Varieties How Do You Fix A Lawn That Has Been Damaged By Evergreen Trees?

How do you fix a lawn that has been damaged by evergreen trees? - spruce varieties

I have recently bought a house) with many pairs of different varieties of pine (pine and cedar trees, in the first place. However, the grass under the trees, not present, not only dead, completely disappeared. The grass is very good in the rest of the place, who had died under the fir trees. What must I do to fix the soil and replant so that the patches are gone naked?
PS, I cleaned the dead needles and now only the bare earth.