This is what they sent me. For 2/3 MS, please sign the transaction with your first BTC private key in your Electrum Wallet. Not sure how to do that.
Ah, so they aren't looking for a signed message to confirm that you're the sender like the SOP for refunds (
OP sounds like that).
The OP is vague, but the new reply has some inconsistencies because why would they need you to sign a transaction for them to return your money back?
The question is: who's "
they"?
And please describe your goal/issue better since this turned out to be an "
XY problem".
Anyways, you don't have to export any private key to sign a transaction.
Just load the unsigned transaction as described by pooya "
Tools->Load transaction":
Click "
Tools", point at "
Load Transaction"; then select "
From file" or "
From text" depending on the format of the transaction that you need to sign.