The phone you want to root is your prime phone while the phone you're using to root your phone prime phone is secondary phone
Setup
Process - Install bugjaegar on Secondary phone, connect otg to it and insert usb cable, connect prime phone to another side of cable and enable otg connection on secondary phone, your prime phone will start getting charge by it, now enable usb debugging in your prime phone and oem unlock too from developer options
Open bugjaegar and allow permission from both phones, to check whether it's working or not do a basic command like pulling down notification panel or rebooting your device