Score the olives. I score them in two places.

Place them in a large bowl with water so that they lose their bitter taste.

Leave them for 15 days while changing the water daily.

When the olives are not bitter when you taste them, strain them and place them in salted water with a little vinegar.

You can store them there and remove small quantities when you need them and place them in oil and vinegar for when you want to consume them.