As is often said, the devil is in the details, and you didn't specify the model of your Catalyst.
Since the connections are not obvious, I'll assume that you have a Catalyst 60, which does not have a MIDI DIN Port.
To use MIDI you'll either need a HOST (a computer, iPhone or iPad), a MIDI controller that doubles as a HOST. or a HOST "box".
Amazon.com: M-VAVE Chocolate Plus MIDI Footswitch Controller Pedal, 4 Buttons, USB Compatible, APP Control, Portable : Musical Instruments
I've never used this, so read everything you can find about it. AFAICT, you should be able to simply connect a USB-B to USB-C cable from your Cat60 to the Chocolate+ and use the wireless app to program it. If you choose to go this way, buy it from a store with a no-questions-asked return policy. It's non-host version gets good reviews on The Gear Page.
If you have an iPhone/iPad (idk about androids) you can connect directly and the iThingy will serve as a host. I recommend getting a powered hub instead of direct connect, else usable time will be limited by the battery in your iThingy. I use this with my iPad:
Amazon.com: Anker USB C Hub, 5-in-1 USBC to HDMI Splitter with 4K Display | 85W Max PD, 1 Powered USB-C 5Gbps & 2 Powered USB-A 3.0 5Gbps Data Ports, for MacBook Pro, MacBook Air, Dell and More (Black) : Electronics
You can also connect a standard (non host) MIDI controller using one of these:
Amazon.com: CME H2MIDI Pro Compact USB Host MIDI Interface | Router, Filter, Mapper, 32-Bit Processor, Dual Power Mode, Minimal Size, For Guitarists & Producer : Musical Instruments
There are other products at various prices in all of the above categories. I suggest that you do your due diligence before deciding which way to go.