Same thing for me earlier today before work. (Being then ... only about 2 hours old with Logic, period.)
I remember seeing the GUI for doing such within Numerology and Ableton Live 9 Intro, but I can't for the life of me find that GUI for doing such, within Logic Pro X.
(It couldn't be something as simple as not having my Roland MIDI interface hooked up, could it?)
Thank you greatly for any pointers.
(Knowledge note: I've been an Atari ST (late '85 to '89) and then PC MIDI user since 1989. I've just moved over to a Macbook Air as well as the above mentioned sequencer software, as well as the Arturia Spark, over the last weeks - learning everything.