Installing PTS is usually a very simple tutorial, but it would take you hours.
Depending on your internet connection and the BW servers’ condition, it will take you between a couple hours to many, many hours. The live game is ~25GB, the Game with PTS is ~52GB. If you have the game already installed, you can add PTS on top of it. At this moment it is not possible (possible, but not easy or recommended) to install PTS on a separate Drive or Partition.
To install and access PTS, follow these steps (or check the video linked below):
1. Download the game client from swtor.com and install it
2. Log in to the client and install the Live game
3. From the button in the bottom left corner open the settings window and make PTS available
4. Wait for the client to download and install PTS
5. Every time when you open the launcher, be sure to select PTS from the new button in the bottom left corner