This tutorial explains how to upgrade to Linux Mint 18. Linux Mint 17, 17.1, 17.2 and 17.3 will be supported until 2019.
If your version of Linux Mint is still supported, and you are happy with your current system, then you don't need to upgrade.
To upgrade to Linux Mint 18 you need to satisfy the following requirements.
Upgrading to a newer package base is not trivial and it should not be performed by novice users.
The upgrade tool only upgrades Linux Mint 17.3 Cinnamon, MATE or Xfce edition.
You need to know how to type commands and read their output. During the upgrade you'll need to understand the output of APT commands.You'll need to understand if a package needs to be removed, if it blocks the upgrade, if it conflicts with another package etc etc.