you haven't specified what you are trying to do. in order to help you, people really need a bit more information:
what are you trying to achieve? do you want the TR to control an external synth (as far as I was aware, the K61 is a controller only)? or are you trying to use an external keyboard to control the TR's internal sounds (or play more than one sound from the TR at once)?
are you aware that the MIDI connection will carry no sound? MIDI messages tell a keyboard what notes to play, what programs to change to, what controllers to change, but they don't convey any actual audio information, so if you want to hear an external synth at the same time as your TR, you will need both hooked up to a mixer or other device. similarly you couldn't get TR or other synth's sounds into a computer just by connecting MIDI cables - you need to make the audio connection too.
Current Gear: Kronos 61, RADIAS-R, Volca Bass, ESX-1, microKorg, MS2000B, R3, Kaossilator Pro +, MiniKP, AX3000B, nanoKontrol, nanoPad MK II,
Other Mfgrs: Moog Sub37, Roland Boutique JX03, Novation MiniNova, Akai APC40, MOTU MIDI TimePiece 2, ART Pro VLA, Focusrite Saffire Pro 40.
Past Gear: Korg Karma, TR61, Poly800, EA-1, ER-1, ES-1, Kawai K1, Novation ReMote37SL, Boss GT-6B
Software: NI Komplete 10 Ultimate, Arturia V Collection, Ableton Live 9. Apple OSX El Capitan on 15" MacBook Pro
connect the MIDI Out on the K61 to the MIDI In on the TR.
set the K61 to the same MIDI channel as the TR's Global (by default #1), then it will play the TR's sounds.
if you want to play different sounds, you have to start making your own combis on the TR, with the K61 assigned to a different MIDI channel (say, #5), and create INT timbres in your combi set to respond to the same midi channel instead of the TR's Global.
Current Gear: Kronos 61, RADIAS-R, Volca Bass, ESX-1, microKorg, MS2000B, R3, Kaossilator Pro +, MiniKP, AX3000B, nanoKontrol, nanoPad MK II,
Other Mfgrs: Moog Sub37, Roland Boutique JX03, Novation MiniNova, Akai APC40, MOTU MIDI TimePiece 2, ART Pro VLA, Focusrite Saffire Pro 40.
Past Gear: Korg Karma, TR61, Poly800, EA-1, ER-1, ES-1, Kawai K1, Novation ReMote37SL, Boss GT-6B
Software: NI Komplete 10 Ultimate, Arturia V Collection, Ableton Live 9. Apple OSX El Capitan on 15" MacBook Pro