How do we start?

HI I need help. I don't how 2 start the adoption process. I've always wanted 2 adopt. I've been married for six years and have 2 beautiful daughters, but I want another child. I always wanted a big family, but my pregnancies are not the greatest. I always thought pregnancy would be so beautiful, but instead it was horrible. I practically lived in the hospital during my pregnancies. It really hit me hard when I was pregnant with my second child, due to the fact that my daughter was 2 yrs old & didn't understand why mommy wasn't home. She missed me so much and would cry herself to sleep becuz I wasn't there. During that time she had Papi and Mima(my mom)& she became so attached to them that it hurt when all she wanted was her father. So I refuse to put my 1st daughter thru that again. I love children so much. I've prayed so much to God and I've gotten so many signs. Adoption just seems right for me. Yes I know many people might say be happy with the 2 you have and I am, but I don't feel complete. If anyone can guide me or instruct me I would be greatly appreciated.