Assisted reproductive technology (ART)
With ART, you take the sperm (either through normal ejaculation or surgical extraction) and use this to impregnate the woman. While this is can be a successful option if you want to have children, it is important to note that it is not actively the same as treating infertility in men. Another problem is that you only have this option available if the sperm cells are healthy and otherwise able to impregnate your partner.
Alternative options include getting sperm from donor individuals, but as you might understand there are several men who prefer to try alternative methods before option for something of this nature.
The treatment is also rather expensive, meaning that this is not always the best option for those couples who cannot afford to lose a tremendous amount of money.