Trying to find a lil more detail for setting up Cron jobs on Linux

I logged in terminal and use the command (i use my real domain name in command)

wget -O /dev/null " www.mydomain.com/index.php?option=com_community&task=cron " > /dev/null

After i ran command, end of message returned back was:

HTTP request sent, awaiting response... 200 OK
Length: 520 [text/xml]
Saving to: ‘/dev/null’

/dev/null 100%[=====================>] 520 --.-KB/s in 0s

2016-08-05 20:21:14 (110 MB/s) - ‘/dev/null’ saved [520/520]

So it seems no errors, not sure what it really did.....on Jomsocial docs, it says to run every 10 - 30 minute depending on how busy the site

1- But how do i set it for 10 or 30 mins? whats it set at now
2 - How do i view the jomsocial cron job ( i read bout setting up cron jobs in general on linux, but cant seem to find the job added by jomsocial
3- I did some test messages between users on site, each user gets the message on site...but in admin panel... Its shows the emails pending ...are these messages pending being sent out to users emails?

Ive tried searching online about this and i just keep finding the 1 section on linux setup in jomsocial doc about sending the command

Thanks

thru trial and error, i was able to get it working....

For me, someone who doesnt know much about this yet, a few more details in the Jomsocial doc for Linux Cron setup would have been good....