If that's from a partnership, you'd make the input on Screen 20.1.  You'd find the input fields on Line 15 for both the partnership's EIN and credit for OH withholdings.  Alternatively, you'd enter an override for "Refundable pass-through entity credit [O]" on Screen 53.121.  Either way, the credit would show up on Line 36 of OH's Schedule of Credits.

If your client was a nonresident investor for the entire year and the only source of OH income was from one or more PTEs doing business in OH, and such income was included on IT 4708, your client would normally not have to file an IT-1040 though.