Okay for all looking for this.
1. Ensure your character has a decent level of both Alchmey & Cooking
2. Open Barrel like a container
3. Place in 1 Yeast ideally ++ however + will do
4. Place in the fruit you require apples, grapes, peaches, pears, and plums. 4 fruit per bottle so for example i wanted 100 bottles so i placed in 400 peach. (Tip- place the fruit in the container in batch's of 100) for some reason 400 at once didnt work
5. Enter context menu and begin Fermentation.
6. Wait a day and hey presto 100 bottles of your chosen drink.
it will add you a year, you just need to name it. for example Dom Perignon Peach Wine 2017
Hope this helps as i have had issues finding this infomation