Heat de wineskin either in the sun or over a radiator.
Rub the seam well.
Inflate the wineskin by blowing gently through the nozzle. Do not overdo it. In the case it offers some difficulty, heat it again.
Fill with a glass of water. Do not worry if some drops of water leak at the beginning. This will happen until the seam tightens and seals.
Pour in some wine and leave it placed sideways for 5 to 6 days so that the wine is entirely in contact with the interior.
Pour out this first lot of wine. It is now ready to be used. For the first few days, it is best to frequently change the wine. Make sure that the inner sides of the skin do not touch during these first few days.