I followed this guide on how to disable the standard Wordpress method of running cron jobs and running it at an interval, but I do not know where to put the code for what I want to be ran when cron jobs runs. Right now the code I want to run is in functions.php and I do not think it is being called at the interval that cron job is set for. I am 100% sure that cron job is set up right, too, for every 15 minutes.
To rephrase, I have cron jobs running wp-cron.php every 15 minutes instead of the standard 'vrtiaul cron' method Wordpress uses. Putting code in wp-cron.php doesn't seem to work and I want to run some code when cron job runs. Where do I put the code?