How do you Make rosemary olive oil?

This would be done by infusion.

You will need a fancy bottle with a good stopper/cork

Take several good stalks of fresh rosemary from you garden and wash well, pat dry and place in clean sterilized bottle.

Decant enough good quality olive oil into the bottle to fill and seal with the cork.

Allow to sit in a cool dark place for at least 30 days or longer. The olive oil will take on the flavor of the rosemary as the herb steeps in the oil.