I pasted the .conf file into Application Support/bitcoin but I need to let the app somehow know that I want to apply the .conf file to it.
Any advice?
Since you are running Mac, and Using CLI to run your bitcoind
These should apply in your case
Sample bitcoin.conf
https://github.com/bitcoin/bitcoin/blob/master/share/examples/bitcoin.conf
default Path to bitcoin.conf
$HOME/Library/Application Support/Bitcoin/
Or
/Users/username/Library/Application Support/Bitcoin/bitcoin.conf
Your bitcoind should read bitcoin.conf from those default paths
Or you could override it using -conf option
example
bitcoind -conf=path_comes_here
Thanks