That thing is a heat pump. It heats and cools. Don't install a big heater until you see how it performs.
You need to run a new, dedicated circuit from a panel (e.g. the subpanel in your garage) just for this unit. That is a standard requirement of all "installed" A/C and heat pumps. And for that matter, water heater, dryer etc. etc. If that's coming as a surprise to you, yeah, everything and everyone should have mentioned that.
You need to hook it to your HVAC disconnect box.
No, it doesn't work like that. There's not like "one disconnect to rule them all". Nope, nope.
Each unit must have its own circuit back to the panel, and its own disconnect (for capacity and circuit-sharing reasons). You will need to buy a disconnect. They're cheap, and you need to make a transition anyway from Romex (which can't go outside) to an MC cable, FMC conduit or wire whip for the last hop to the vibrating appliance. So you were going to mount a junction box anyway, now you spend $4 more and get a disconnect.
Each unit's disconnect must be near the unit and in plain line-of-sight to the unit. Why? So this doesn't happen: "why is it my heat/cool not working? Ah the disconnect is pulled, I'll just reconnect it now" OW OW OW WTH MAN? "Sorry, I did not see you working on the unit, since it was 50 feet away / around the corner of the building / behind a bush / etc. etc.")
Note that somewhere there is an A/C or heat pump, there must be an outdoor receptacle within 25' of it, because that's how long the cords are on vacuum pumps. DO NOT make this a "dedicated outlet to the heat pump" - place the outlet where YOU will most likely to get useful use out of it. It simply needs to be within the 25' cord radius. The reason is this plug will only get used for HVAC service every 10 years, and outdoor GFCIs don't last that long LOL, so it'll be dead everytime the guy goes to use it. Like any 120V outdoor outlet, it needs to be GFCI but can be protected from an outlet or breaker inside.
The Codebook is currently "highly in flux" as to whether GFCIs are needed on heat pumps (which include air conditioners; a traditional A/C simply lacks the $10 reversing valve needed to let it also heat). The problem is, some companies in the A/C industry aren't ready and aren't able to manufacture A/C units that don't trip GFCIs.