To set the saddle height, wearing the shoes you will be using, sit on your bike leaning against the wall or have someone put the front wheel between their knees and hold the front of the handlebars.
Put both feet on the pedals and pedal backwards until one of your feet is at the bottom of the pedal stroke.
Move that foot forward so your heel sits on the pedal, you should have a straight leg. This is so that when you're pedaling on the ball of your foot, you have a slight bend in the knee. (About 5 degrees).
If your heel can't touch the pedal, then you will need to lower the seat. While having your heel on the pedal, if you still have a bent knee, then you should raise the saddle.
You may need to go through this process a number of times to get it right.
Most seat posts have a maximum adjustment point. Never exceed this as there will be insufficient seat post inside the frame, which could lead to the frame splitting or the seat falling out of the frame.