How to add a cron job

It’s a pity the information on some pages is so shallow.
I like to use two-way-synchronisation and it seems that there has to be add a syntax to a cron job. But i can’t find information how to setup that kind of syntax.

*/2 * * * * wget -O – https://salonbookingplugin.it/wp-cron.php?action=sln_sync_from_google_calendar&>/dev/null

Where and on what way does it need to setup??
I subpose the wp-cron.php file, but the lines mentioned above need more …..

So please try to make the how to pages more clear for general users.

A warm welcome for any help.

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