To extend what @IPANetEngineer said (because you said you're new to MT world and I don't want you to get impression we're a bunch of unhelpful nerds here) ... the steps are basically like this:
- download winbox tool from download.mikrotik.com ... even though it's name implies windows, the executable runs inside wine environment on macOS or Linux just fine
- if you haven't already, upgrade ROS to 7.2.3 and install wifiwave2 package (from extra packages)
- reset device with no config at all
- use winbox and click device's MAC address to connect ... username will be admin and password will be empty
- create a bridge
- add both ether ports and all 3 wifi interfaces to bridge
- configure device with LAN IP address (bind it to bridge interface) and set your router's IP address as gateway for default route
- configure wireless (security profile, SSID, ...). wifiwave2 allows pretty wild security profile setup, but in 7.2.3 it's a bit buggy (apart form basic WPA2 config) ... so stay with authentication-types=wpa2-psk encryption=ccmp group-encryption=ccmp to make sure most (if not all) clients will be fine.
From what's written on forum (or rather from what's not), it seems 7.4beta might be fine (and fixes a few wifiwave2 bugs), but 7.3 doesn't seem to be stable. 7.2.3 is very stable for me hence that's what I'm suggesting to install.