Well, your ISP router should be running a DHCP server, which you want to keep as “authoritative”.
You can set the Mikrotik as an AP bridge (i.e with all intefaces, including the Radio/Wi-Fi into a single bridge, with only one ether interface - advised - kept out of the bridge for emergency access).
You can then put on the bridge the DHCP client.
This is the simpler solution, but - in my little experience - and it depends on the devices involved - it may create issues in some cases.
Personally I would limit the IP pool of the ISP router and assign a static IP address to the Mikrotik router (please read as switch) bridge.
So:
On ISP router:
set DHCP server to an IP pool of (say) 192.168.1.2-192.168.1.249 netmask 255.255.255.0
On the Mikrotik:
FIRST thing:
Make sure that ether1 (which is usually WAN) is marked as LAN
Assign to it the address 192.168.1.251/24
Before making any other change, make sure that you can access the L0009 when connected directly to ether1 with Winbox via MAC, AND via browser/Webfig after having assigned temporarily to your PC address 192.168.1.252 netmask 255.255.255.0.
THEN:
Create a bridge and add to it interfaces wlan1 and ether2-ether8.
Make sure that the bridge is marked as LAN.
Assign to it the address 192.168.1.250/24
Configure the wlan1 as “ap”, add SSID, authentication, wi-fi password. (unless you really need it, avoid using WPA3 as it has reported to be giving issues with many devices).
That’s basically it.
Strictly speaking both the bridge and ether1 should not need an IP address assigned, as through Winbox you should always be able to access both via MAC, but this way you can use also Webfig or SSH.
Since you are using a bridge, you can disable or remove anything in /ip firewall.
If you get to this point, we can later discuss of further needs/requirements, in any case once you have a basic configuration (fully working or not) follow this post:
http://forum.mikrotik.com/t/forum-rules/173010/1
and provide your (anonymized) configuration, so that it can be used as a base reference for fixing possible mistakes/fine tuning,/etc.