Both. Basic concept is you put it in when you first assemble the must to kill wild yeast. 12 hours later you pitch pectic enzyme to remove pectin. 12 more hours later you pitch yeast. (This is usually done in a bucket with a breathable cover so the pot meta can dissapate.) After fermentation is complete and wine has cleared rack off of yeast and add pot meta and pot sorbate to kill remaining yeast.
I would suggest you read a bit more. That is only a first early concept. Somewhere in there you have to put it under airlock( I do at about 1.030) and nutrient must be added, acid checked, gravity measured... And if things need fixing, like it won;t clear, ferment, bubble you need to understand why. I am not trying to scare you, just give you the full tool kit you need. Too many posts here are after the must is assembled and yeast pitched someone has a problem and asks "Can this be salvaged?" There are many posts on how to do it, some disagree with others. Read as much as you can. I woould prefer you get a satisfying hobby, I don't want you to start out thinking you threw a lot of money away on a dumb idea. Many here have had to pitch a batch or two (or more) and with later experience now know why. Much of that could have been avoided. If I had known more about my first batch, I would have known the sugar on the instructions was too much and would never ferment out. That batch went down the drain and did not need to. Make sure you have the basic tools you need, a hydrometer, and unless you are working from a packaged kit, a ph meter. Read about and take seriously the sanitizing procedures, vinegar or bacteria science experiment is a lousy outcome. Some recipes are better, more complete than others, know your source. Watch temperatures, too warm and you get rocket fuel and ruin the wine.
Chances are you know someone who does this and will take the time to talk. When I started beer, I found 6 people at work who dabble. Or join a club.
