You can call your local SRS and they can possibly give you information on what agency you can go through. For my husband and I we had to go to an informational meeting now we are going through a 10 week training course. They will want to do a tour of your home to see if it is a safe place for a child to be and you also have to have a background check. And I know you have to take a CPR class. I hope that helps.
I just googled foster care in st. louis missouri and got these links:
www.foster-adopt.org stlouis.parentzone.com/parentresources