How to reach Plane of Fire & get out
You can find the zone in for Plane of Fire in eastern Plane of Tranquility -- a little bit out into the ocean. Inside the large hut that protrudes out into the eastern ocean you'll find a large floating ball of fire inside a pool of water, shown in my picture above.
To enter the zone, click on the large ball of fire. If you meet the requirements to enter (meaning you've completed the sufficient PoP flagging) you'll zone into PoFire. Otherwise you'll get an error message. Keep in mind that if you're reading this many expansions ahead of PoP, the flagging requirement may no longer be there.
If you still need help locating PoFire I recommend you take a quick gander at my map below. The zone in location for PoFire is marked with a blue circle.
As per usual once you're inside Plane of Fire there's no clear indication of how to leave. Luckily you have me! When you're ready to bail from this zone you'll want to click on the burned up tree nearby where you zoned in at; the tree is shown in the picture below.