K.B.
Contact the local adoption agency. If you go through the state your cost, if any are low. An adoption agency, and depending on domestic or international, your cost are high.
Meet with several agencies. You want to like the people you will be dealing with. After you determine which agency you want to use, they will provide all the necessary paperwork to fill out. We used Bethany Christian Services. They were great, and our adoption took 8 weeks.
Afterwards you will need to gather all your financial records, get medical exam & blood work completed, fingerprints, and you will need to create a family album. You will need to get recommendations too.
Also, decide what "type" of child you are looking for...special needs, cultural (race), gender, age,. etc.
I wish you well in this endeavor. It is WELL worth whatever expenses. You might think you are doing a "favor" to "save" a child, but believe me, we are the blessed ones because of our daughter. She has enhanced our lives tremendously.