How to setup proxy server after the mikrotik router?

Hello ,
I have a reverse proxy server that running on cloud and it’s working (with public IP),
and the router use ppp-out connection

what do I need to setup inside the router so all trafic from the Wlan will go throw the proxy ?
the device is :
ethernet - 10.0.0.1/24
ppp-out - dynamic IP , default route
wlan 172.16.100.254/24
dhcp (for wlan only) 17.16.100.10-50
firewall masquerade chain=srcnat
very simplae setup of router - just give free internet to my office guest

Thanks,