I would rehydrate the yeast per the instructions on the packet.
In the meantime, I would then make a yeast starter of 1/4 cup sugar and 2 cups of of water. mix that well (you want to incorporate a lot of air), and add the rehydrated yeast. Add some yeast nutrients if you have any.
Shake every hour or two to mix in more air. After 12 hours, pitch that into your must.
The purpose of making a starter is that the alcohol in the must is not so good for getting yeast going. The starter will give you a nice colony of yeast before it hits the main course.