MACOS set up mitm web tranparent model

Hi, I am current trying to use mitm web interface on my mac. And I use ettercap for arp attack, after choose the target, how to set up transparent model for mitm web interface?

Place the following two lines in /etc/pf.conf.
line 1 mitm_if = “re2”
line 2 pass in quick proto tcp from $mitm_if to port { 80, 443 } divert-to port 8080

when i try to copy paste line 1 and line 2 in my /etc/pf.conf. it says file read only