Greetings.
An apostille is an official government document that validates that the “signing authority” of other documents such as birth certificates, marriage licenses, and - in your case - transcripts, are true and valid. In the US, the apostille must be requested from the office of the Secretary of State for the state in which your document originates. So if your birth certificate is from Oklahoma, the State of OK, Sec of State will issue the apostille. (as an example visit this New York url for more general info http://www.dos.state.ny.us/corp/apostile.htm or search your own state’s Sec of State/State Dept web site).
Steps I took for OK birth cert and CA marriage license apostille>>
1) obtain official document
2) send original to Sec of State (cover letter and fees)
3) make copies!
4) have both documents translated
5) submit with application process
Hope this helps