How do I enable Territory Management?

How do I enable Territory Management?

The how-to says 

To enable territory management

  1. Click Setup > Territory Management > Territories.
  2. Click Get Started. You will have the following options to create a territory hierarchy.
    • Extend from Role Hierarchy - Click to replicate the hierarchy from roles to territories.
    • Start from Scratch - Click to create territory hierarchy from scratch.
However, there is not option for Territory Management in my Setup. See screenshot and please advise.