Here's a step by step from a Lallemand document I have:
How to Hydrate Dry Wine Yeast using “Go Ferm” (A Recommended Nutrient Regimen):
1) Using clean water (filtered or distilled is best), calculate the amount needed and heat it to 110 degrees F (43 degree C).
2) Add the required amount of “Go Ferm” to the heated water. Mix it in well so that there are no clumps, and let it stand until the temp of the mixture falls to 102 degrees F (39 degrees C).
3) Add the required amount of yeast to the mixture. Stir it to break-up any clumps and wait 15-30 minutes.
4) At this point you will want to add a portion of the must/juice into the yeast mixture that is ½ to equal the volume of the yeast starter. This helps the yeast become accustomed to the pH, TA%, brix level (sugar), and the temperature of the must they will ultimately be fermenting, and is done to avoid shocking them.
5) After a 10-15 minute wait, the yeast should now be ready introduce into the must!
This process is recommended to be done once for every difference of 15 degrees Farenheit. So if your must is 70F and your yeast is 104F you would do this twice.
Hope that helps,
Oskaar