I would assume the OP already has a bike and is inquiring about improving his fit by himself. There are essentially 4 elements to bike fit:
1) Saddle height
2) Saddle fore-and-aft position
3) Reach
4) Bar height.
You want to tackle them in that order.
1) Google "heel on pedal saddle height.". Read a few of the results, then apply.
2) Google "saddle fore and aft balance". Watch this video:
After adjusting fore-and-aft position, reset saddle height.
3) Sitting stationary on the bike, hands on hoods, elbows slightly bent, back straight, your reach is correct if your upper arms make a right angle with your torso. One changes reach with stem length. Move your hands around and guess at a more correct stem length. Stems are pretty inexpensive and a zillion options available on Amazon.
4) Bar height is personal. Neither lower nor higher is necessarily more comfortable. Lower is obviously faster, so start with that and see how that goes.