Just to add to George's helpful response, you will need to obtain from your client details of the transaction from purchase to sale like you do with your domestic clients.  You will only be able to extract the amount for gross proceeds but not much else from F.8288 or F.8288-A because those details are not required - if your client had filed a F.8288-B, that would be more helpful.

The input you make for F.8288-A will flow to 1040-NR but not 1040, if that's what your client files.