Hey, make sure your DAW is configured to send clock and possibly other transport messages to Midihub. You should place a FROM USB X, select it, and verify that you’re seeing non-0 BPM value in the MIDI Monitor pane of the editor. If you do, then the DAW is set up correctly to send the master clock to Midihub.
The next step is to make both the MIDI notes and the start & clock messages reach the Arpeggiator pipe. If you’re sending notes from your DAW, then it’s easy, place it like this:
FROM USB X → Filter (keep only note on, note off, start, clock, stop) → Arp → TO USB/MIDI X
If you want to use master clock from a DAW, and notes from another input, you have to use a virtual bus, do it like this:
FROM USB X → FILTER (keep only start, clock, continue, stop) → TO VIRTUAL A
FROM USB/MIDI Y → FILTER (keep only note on, note off) → TO VIRTUAL B
FROM VIRTUAL A → TO VIRTUAL B
FROM VIRTUAL B → ARP → TO USB/MIDI Z
The virtual bus A is dedicated to the sync messages. The virtual bus B is for providing notes, as well as sync messages, merged into a single stream, and sent to an output port.
The MIDI stream merging and virtual buses are explored in a bit more depth in the How To’s section: How-To's - Blokas Community
Also check out how to use Arpeggiator with Midihub’s internal clock: Arpeggiator not work - #2 by Giedrius