With every new expansion that an MMO launches, it's almost guaranteed to have its fair share of bugs and problems. That said, Guild Wars 2: Path of Fire is riddled with issues that aren't just annoying, but actually will hinder your ability to play the game.
In our time with Path of Fire, we were constantly bombarded with bugs that kept us out of the new map areas and even blocked us from accessing the initial story content. Even when these issues are inevitably dealt with in the future, the actual process of accessing the Path of Fire story content is still troublesome and confusing.
Firstly, to access the content you don't actually need to have finished the base story or the first expansion Heart of Thorns in order to start Path of Fire. However, you do have to be the max level of 80 to unlock the expansion.
You begin by going to your Hero panel. From there, you select your story journal. Under that, you will find the Path of Fire story on the left side of the menu screen. Choosing it will give you the option to start the expansion.
Once began, you will be given a letter. You will need to go to your mail inbox and read it. This will give you the first objective of traveling to Lion's Arch. Follow the mini-map quest marker in the city to the Captain's office. Once there, enter the instance and speak with Captain Ellen Kiel.
Follow the captain as she speaks with you. Once she is done, leave the instance. Continue following the quest marker through Lion's Arch to the southern circle below Sanctum Harbor where you will find a docked airship.
In front of the airship, greet the First Mate Fidus Foecrush, which will allow you to go aboard. Path of Fire will then give you the option to enter the instance, which will begin a cutscene that introduces you to the Crystal Desert. Complete the proceeding tutorial mission and you will unlock the map and story for the entire Path of Fire expansion.