I have the omnibus f4 pro corner and this esc-
https://www.banggood.com/Eachine-Stack-X-F4-Flytower-Spare-Part-35A-4-In-1-ESC-2-6S-BLHeli_S-Dshot600-Ready-For-Racing-Drone-p-1220191.html?rmmds=search&jumpAuth=ace50bd2
Where do I solder the battery wires- to the fc or to the esc?
Since the Esc has a build in regulator that poweres the FC, you will need to solder the battery wires to your esc
Luca 
Yeah as @luca said. Connect batter wires to the ESC, then that wire harness needs to go to your omnibus. The order will depend on the pinouts of your ESC as it might not plug in directly.
If you need more help I can look into it later as I am just on my phone right now
Fine. But why don’t i solder it on the omnibus f4 pro corner?
Because you dont need to…
Your 4in1 Esc provides power to your Fc.
The “bad” thing is that the Omnibus F4 pro Corner is made for 4 single Escs and not a 4in1 esc…
But it should still work 
Its nearly plug and play…
You can also solder your battery wires directly to your Fc and power the 4in1 ESC off the flight controller…
Your Choice and probably only a cosmetic question 
I would connect to the ESC’s and keep the main voltage away from the FC.
As well the FC is equipped with a OSD not feeding direct battery voltage into the FC may also provide a cleaner FPV feed.
Feeding the ESCs battery power directly could have a better results then pulling all those amps through the FC first.
I think at the end of the day its your choice. The FC can take the voltage.
Personally I would attach my battery input to the ESCs
Good points and I do agree it is generally best to keep high voltage away from FC if possible… except if you want to use the current sensor on the omnibus then you do need to make sure the battery circuit passes the current sensor first. So if you want to use the current sensor, then you do actually need to connect your battery via the FC first and then to the 4in1 ESC.