I was unaware myself once upon a time too... no, no, just kidding (well I was but, that was said jest).
Welcome!
I don't know if you know, but the latest version of Linux Mint is I believe 18.3, so you may want to consider upgrading to that.
If you would like to experiment with Kali, you should read
this, there's a link down the bottom of that page, that would be good for you to get started with Kali. Although, I do strongly suggest you get familiar with Linux Mint first before trying Kali, as this should give you the foundational knowledge to be able to move to Kali without such a steep learning curve.