To run a command via cron every 5 minutes:
*/5 * * * *
* any value
, value list separator
- range of values
/ step values
For example
Run at 15 and 45 past the hour, every hour:
15,45 * * * *
Run at noon, once a day:
0 12 * * *
Run at 2pm, every Monday (dotw == 1):
0 2 * * 1