I was asked to authenticate my birth certificate at Nigerian embassy in Washington by Bahamian authorities how do I go about getting it done I'm in the Bahamas.

Submit the birth certificate if you are sure of the birth certificate, are you a citizen ,or green card holder,all this birth certificate issued, has been clarified, during Green card holder ,citizenship, is does not come up like a request, something is fishing underneath. Please check the person properly,sincerely

I don't have visa to visit the US, that's the problem

You have to return to DC for that to be done