You have two options:
1) Contact our 24/7 live support team on loive chat and they will add note to the order, so the designer sees.
2) You can paste the drawing request directly on the revision page yourself .
Find the Revision page link on "My orders" Page inside app
Click link in the "Revision column" for the correct order
Add note on the page, and press "Request Changes" , our designers will see it.