How do i get married to a female and have children, being gay?

Insemination: Since you are from nigeria my understanding of world politics says you might need to leave the country for safety. In the us in most places you don't have to marry a woman but can adopt alternatively artificial insemination is another option with a surrogate mother who would carry and deliver the baby (expensive here).

Being Gay: Please do not bring a female into a life with a lie or for the purpose only to be a mother to your children. First i would recommend you find a partner that wants the same thing and then find a way to adopt or to find someone willing to be a surrogate for children for you. This may be easier to accomplish in europe or in north america.