Time to mix. When you turn on your mixer keep it on low (the first two or three settings) until you start to see some foam. You can up it a bit from there. Gradually turn it up. You want the whipped cream to form stiff peaks, so watch is carefully so you don't over whip.
Once it's ready, it can be used immediately, or It can be stored in an airtight container in the refrigerator for about 2-3 days.