To add the privilege to instruct for the Aerobatic Rating an FI(A) only has to demonstrate competence to do so.
It is assumed competence to actually fly aerobatics already exists. No pieces of paper required, no minimum hours etc.
However:
FCL.905.FI FI — Privileges and conditions
The privileges of an FI are to conduct flight instruction for theissue, revalidation or renewal of:
.....
(f) a towing or aerobatic rating, provided that such privilegesare held
An instructor can only instruct for a rating they themselves hold. So, if you do not already hold one, you should ensure you meet the requirements for an Aerobatic Rating and apply for one at the same time as applying for the instructional privilege.