You can log into the National Student Clearinghouse site after the 3rd week of classes to obtain an enrollment verification letter: https://apps.qc.cuny.edu/studentclearing/
If your institution is requesting an official signature or stamp, please share this website with them so they may make their request on your behalf.
You can also print your enrollment status letter, at no charge, by logging into CUNYfirst and select the Student Center tile. Open the Transcript and Verification tile and select the link for Request EnrollmentVerification.