For DCPS, the role is the 504 coordinator.
Google the name of your child's school and "504 Coordinator" and you will find out who to reach out to.
Example - Jackson Reed 504 coordinator gets you this page:
https://jacksonreedhs.org/apps/pages/index.jsp?uREC_ID=613512&type=d
Next - send an email that your child's pediatrician had referred your child for an evaluation and your child has an ADHD diagnosis. That their ability to access the general education curriculum to the same extent as nondisabled students is impacted and you would like a meeting to understand the process for your child getting accommodations to enable them to access the general education curriculum.
It is very important that you ask for a meeting as DCPS needs to meet within 15 days of your requesting the meeting - but is really good at making excuses as to why now is not a good time.
https://dcps.dc.gov/page/section-504-process