This is really a linux question, not a Raspberry Pi question. The answer would be the same in just about any version of linux or unix.
To add a cron job type
If you want more info on how to add a cron job, how to specify the times, etc, then you can google it or man it.
Your command will probably look like this:
if you want more info on wget you can type
You could also use curl.
In general, you use curl if you are just looking to test the connection, and wget if you actually want to retrieve something.
Hope that helps.