And thats where you lost me....told you i was new to midi
First, you need a midi interface for the Amiga, which the most common are Parallel Port Midi interfaces. I think, but am not certain, that the Deneb (and maybe Highway/Subway variants) USB card supports USB Midi devices under Poseidon.
After you have a MIDI interface for the Amiga, then you can hook the Amiga and MIDI keyboard together with standard 5-pin DIN MIDI cable.
Software on the Amiga can allow the Amiga to send MIDI notes to the Keyboard (hooking up a MIDI cable from the MIDI OUT on the Amiga, and to the MIDI IN on the keyboard) or to input notes on the keyboard and have them be played or recorded on the Amiga (hooking up a MIDI cable from the MIDI OUT on the keyboard, to the MIDI IN on the Amiga). If you've got two MIDI cables, you can transfer MIDI information in both directions.