Multisig help on coinb.in need assistance signing never done this before. this has me stumped for 2 days.

As others have mentioned, it’s the raw unsigned transaction hex that goes in that field. Did someone direct you to use coinb.in to sign a transaction? They should have provided the raw transaction. Before you sign anything, be sure to verify and understand what you are signing. You can view and verify the raw transaction at coinb.in using the Verify tool. The transaction output(s) should include your receiving address and expected btc value.