New installation on Raspberry Pi need to change http port

[jordanthompson]

Hi all,
new user. I have installed nagios 4 on my raspberry pi that also serves my web pages on ports 80 and 443. I'd like to set up nagios to listen on something like 8080. I have searched everywhere and there are references to it being able to be done, but no decent how-tos.
The other dilemma I have is that I don't want to break my current installation of apache.