Hello world, newbie question

I have just installed OpenWRT on 2 Ubiquiti Unifi AC devices (not AP).
As a newcomer, I would like to do a simple "hello world" setup, in which I take 2 computers that talk to each other over these devices with static IP configuration (can be ip version 4, I don't care).

What would be the most straightforward way to achieve this using UCI or LUCI?

The simplest way to get a "transparent" wireless LAN bridge is with WDS. Set one unit to have an AP(WDS) radio interface and the other one as Client(WDS). Make sure both units have different IP addresses but in the same subnet range (e.g. 192.168.1.250 and 192.168.1.251). Then bridge the radio interfaces into the LAN network.

Static IP addresses, no dhcp, no WAN, just two computers talking to each other.

And disable the DHCP servers in both units, since the network is under control of an existing main router providing DHCP.

Thank you for the information!

Is it possible for both sides to be stations? I do not need other clients connecting to the AP, just bridge between two computers.

To have WDS between 2 devices you have to have one AP so that the other one connects to it.