Hi Mmelindas,

You should set your seat height based on how much bend is in your knee- you want just a slight bend at the knee when your leg is fully extended.

If you are shifting side to side while pedaling, that's a sign that the seat is too high and you have to reach down with your leg.

Now with your kind of bike, I don't know how adjustable, front to back, the saddle is, but normally, when your pedals are horizontal, the forward leg should have the tibia straight up and down. You move the saddle forward or back to achieve this.

Nanci