It is tradition in the United States to wear an engagement ring, as well as a wedding band, on the left third, or "ring" finger. Normally, once married, many people will wear both rings, referred to as a wedding set, on the left third finger. Hopefully this answers your question, and if you're the one wearing it, congratulations!
Tradition dictates that the engagement ring goes on your left hand, next to your pinkie finger. This is true for most Western countries, however there may be some countries that customarily uses the right hand or another finger. The left ring finger has always been believed to lead directly to the heart, hence the tradition of wearing the ring there.
An Engagement ring goes on the ring finger of your left hand. It was thought that there was an artery running through that finger that went straight to your heart. This is the same finger that you will wear the ring once you are married. Good luck in the future.
Traditionally, an engagement ring belongs on the ring finger of the left hand. The ring finger in located between the pinkie finger and middle finger. However, in Poland and a couple of other Western European countries the ring is to be worn on the same finger of the right hand.
An engagement ring goes on the same finger that the wedding ring does, the left ring finger. Most of the time when people get married (at least for the woman), the wedding band will be soldered to the engagement ring and they will be worn together on the left ring finger.
The custom in the United States is to wear it on the left hand, second finger from the pinky. This is the same finger that you would eventually wear your wedding ring on. In fact, you can use the engagement ring as your wedding ring to save the cost of getting a wedding band.