Exim append disclaimer message to body of incoming emails

Hi, I need a solution where absolutely all external incoming emails have 2 lines of text appended to the body of the email. I searched on google and found there's a tool called altermime that can be used with the exim transport_filter setting but I do not know where exactly to use that: transport_filter = /usr/bin/altermime --input=- --disclaimer=/etc/exim_footer --disclaimer-html=/etc/exim_footer_html
Can someone please help and guide me where should I add the above so only incoming external emails have that appended? Thanks in advance.