How can i claim refund of federal tax withheld by the irs?

I hold a merchandising account on Amazon Inc US and receive royalties from it. As per the Indo-US tax treaty, Amazon withholds 15% of my royalty every month. Amazon also issues me a form 1042-S every year stating the total royalty paid and the total amount withheld.

Since I already show this royalty on my ITR filings in India, can I get a refund of the amount withheld by the IRS? If so, what is the procedure for it?

Thanks