form SSA 1042S

I am a US citizen living abroad and the SSA withheld by mistake $1350 on my SSA benefits, until I proved that I was a US citizen. I received the form SSA-1042S and in box 7, it shows $1350. The publication 905 says " If the SSA is unable to send the refund to you before the year ends, you must file a federal income tax
return to get a refund of this tax".
Where can I enter this amount in Turbotax to get the refund as form SSA-1042S is not supported? For now, I put the $1350 in box 6 as a Voluntary Federal Income Tax Withheld of form SSA-1099- Is it possible to do that? Thanks