In the command line type
crontab -e
5 * * * * /usr/bin/lynx -source <a href="http://yoursite.com/cron.php
And now exit: press escape and type ":exit"
By exiting you are saving and you wont be prompted.
Links
[1] https://dominiquedecooman.com/blog-topics/linux-0
[2] https://dominiquedecooman.com/blog-topics/cron
[3] http://unixhelp.ed.ac.uk/CGI/man-cgi?crontab+5