How can i slow my heart rate down if it's 137?

Heart rate vary's greatly depending on what activity you're doing. Is the 137 your rate right after exercising, or is this is a typical rate? I'd suggest measuring your resting heart rate (when you're relaxed) several times throughout the day, for a few days. If the average is high, over 100, then I'd see a cardiologist. There are med's such as beta-blockers that can help slow your heart rate.

Heart rate varies during the day, adjusts to perceived needs. Relaxing helps and a typical resting heart rate would settle at less than 100/min. If your heart rate at rest is consistently over 130/min talk to your doc to have it addressed.