Figure out the square footage of the area that will be seeded. Use that information to calculate how many rolls of straw erosion blanket to buy; blankets usually come in 4-foot by 56-foot rolls. For each roll of that size, you'll need about 50 yard staples.
Spread the seed over the area to be planted. Cover the seeded area with strips of the erosion blanket. Cut the strips to length with scissors. Because the erosion blanket is easily cut, you can shape it to fit around trees and other landscaping. Keep the strips as close together as you can without overlapping them.
Secure both edges of the erosion blanket with a yard staple placed every two feet along each edge. If the staple doesn't push into the soil easily by hand, use a rubber mallet to tap it in.
Water the lawn as you normally would. The blankets will biodegrade on their own, so won't need to be removed. This will take about 45 days. Once the grass is thick enough to withstand walking on, remove all of the staples.