After logging in to the Unified Portal of the employer, simply copy and paste the link I have provided in the reply. It will open the page for filling out the branch details. Fill out the information correctly and submit. If you encounter any issues, there is a specific help file provided by EPFO.
Managing EPFO for Multiple Branches
When an establishment chooses to operate under the same PAN identity/management, meaning branches of the business at different locations within India, and pays the EPFO, they must either manage it centrally at the head office or opt for branch-wise/location-wise management with subcodes. They need to correctly fill out and submit the Form 2 online. Upon successful submission, the department will communicate with the principal via email.