An ideal situation for a breast implant is when the breast is drooping mildly and the nipple is still near the center of the breast and not pointing downward, there is some visible skin beneath the nipple and you are satisfied with correcting the size only and happy with the shape and contours you have.
You can also check yourself whether you need a breast lift in addition to increase in your breast size. In case where your nipple is below the level of the crease under the breast then a breast lift becomes necessary for you. Also, the distance from the small notch at the base of your throat to the nipple should be 18 – 22 centimeters maximum ideally and if the distance is more than that a breast lift is the only answer to your question how to increase breast size. A surgeon can suggest you which surgery you should opt for in order to increase your breast size after making due diligence.