If you receive an office action from the USPTO with a transliteration requirement, it means the Office is requesting you to provide a transliteration of your non-Latin characters or foreign-language text included in your trademark application.
The USPTO often requires transliterations to ensure it can properly assess trademark applications with non-Latin characters and search for similar marks in its register.
You can submit the transliteration statement online. Bear in mind that if you filed your original application as TEAS Plus (a type of application allowing for custom goods and services items to be submitted), your application will lose this status and be treated as a TEAS Standard application. As a result of losing your TEAS Plus status, you will be required to pay a processing fee of $100 per class.