Help needed to make ONT forward WAN connection to other router

Hi, im sorry for the confusing title of the post, i couldnt find the right words to explain it in a sentence. The problem i need to sort out is i recently got a fiber connection from my isp and they gave me a huawei ONT which is also acting as a DHCP Server to provide ip addresses to devices that connect to it. Now i have a seperate router (ubiquiti's unifi udm pro) which is what i want to use to act as a DHCP server since all my other devices in the house are connected to it and getting ip addresses from that. What i want to know is how do i stop the ONT acting as a DHCP server and provide the WAN ip address to the UDM Pro so it can basically act as the main router.Hope i am able to explain my issue. Thank you and looking forward to your reply.