Do you have Ubiquiti Unifi software installed somewhere?
You can run it on any PC (Windows, Mac or Linux). It doesn’t need to be running 24/7 for your AP to work but you will not get performance stats while the software is not running. There’s an addon for Hassio if you’re running that.
As @tom_l suggests there are a million vids on how to set up. Things to keep in mind keep your channel width down you don’t need the entire spectrum for access and try to pick a channel that is far enough away from the wireless you already have running. You have selected probably the world’s easiest ap to setup you’ll be an expert in 30mins of setup.
The Unifi controller has options to setup a SSID to a specific vlan tag, outside of that depends on the abilities of your switch/router to direct that traffic.
Previously, I tried a Mikrotik AP ( Mikrotik RB941-2ND-TC) and there I was able to define VLANs using different network address range and the redirect to the same network range of the main router.
As far as I understood, the AP is not capable of this, but needs something else to manage it, and then it can use it.
So, I will just use it as a “simple” AP, knowing that if one day I wnat more, I have to buy more…