Thank you po-Unlock mo muna yung bootloader
-Then download ka na ng desired custom rom mo
-Pwede mo siya i-install via adb, fastboot, twrp/recovery, or any kind of app seach ka lang tutorial sa google madami lumalabas
Take note: Di na recommend na magroot before na mag custom rom kahit di root pwede
Do at your own risk parin, search search lang kaya mo yan