How do I upgrade my graphics card?

I have a 13 inch, 2015 Macbook Pro.

The graphics card is not working well. I play World of Warcraft. I have my in-game settings as low as possible and it still has trouble running. People who use much less expensive Windows devices have no problem running the game on the highest settings. It's infuriating to know that my laptop can't perform on par.

I want to be able to play the game smoothly on the highest settings, but it seems like upgrading the graphics card is made really hard to do by Apple.

I want to know how I can do this.