You may either pin down staples with your hand, hammer, rubber mallet or some special tools like a staple setter / driver.
Installing tips (1)
When the ground is hard it may bend the staples by putting them in with your hand or hammering, Pre-drill starter holes with long steel nails that will ease the installing of staples.
Installing tips (2)
You may choose galvanized staples if you don't want them to get rusty soon, or black carbon steel without rust protection for additional grip with the soil, increasing holding power.