If you give your girlfriend a promise ring with the intention of engaging and marrying her in future, then the ring is worn traditionally on the third finger of the left hand. If you are giving a promise ring to someone you don’t want to marry, the ring can be worn on a finger of the right hand.
How does one give a promise ring?
How to Give a Girl a Promise Ring
Can a girl give a guy a promise ring?
A man can give a commitment or promise ring to his significant other and so can a woman. (Of course, men and women can give and receive engagement rings too, but it’s more common with promise rings. )