You didn't mention the scholarship because you didn't mention it when you applied yourself. If you have received the admission notice, you can submit it now. But in this case, the school may have to reconsider, because if you don't mention it when you apply, the school will think you don't need it.

If your qualifications are really good or you want to get a scholarship, it's no harm to mention it now.

I don't know if you study liberal arts or science and engineering. If it is liberal arts, it will be troublesome, but science and engineering, the problem is not big. Because almost all doctoral students in science and engineering have scholarships.