In Lower La Noscea (Moraby Drydocks), there's a boat that can take you the Wolves' Den. That is where you unlock most (all?) of the PvP stuff.
There are a few different PvP modes.
• The Feast : Two teams of 4 members compete against each other. There's some additional nuance here -- something about picking up medals. I don't know much about it.
• Frontlines : Three teams of 24 members (or 8, if there aren't many people in queue) compete against each other with specific goals in mind (capture the flag, kill each other, do the most damage to XYZ)
• Rival Wings : Two teams of 24 members compete against each other to destroy the other team's tower (and killing each other along the way)
• 1-on-1 fights : In the Wolves' Den, there is a "training area" of sorts. I think (though I've never personally done it) you can challenge someone to a fight in that specific area and you can essentially duel each other. Maybe you can just freely attack anyone in that area? I don't know. I've never actually seen anyone over there. It's the area in the Wolves' Den with training dummies.
Gear and level does not matter during PvP. You can go in literally naked and it will not affect your performance. Also, you can go in at level 30 and you will perform identically to someone that is level 70 (this is because PvP has its own action set).
Other random tidbits...
- The Feast generally doesn't get a whole lot of people queuing for it.
- PvP does award exp, tomes, PvP-specific currency (mainly used to purchase glamour gear), and a large variety of achievement rewards. You WILL encounter people that don't actually care about their performance, they merely want the rewards.
- The last time I participated in PvP, there were a fair number of bots.
- There is a "frontlines roulette" (despite it being literally identical to queuing for frontlines manually, but the roulette does grant extra rewards daily), so frontlines tend to have the highest population running it (and thus, the shortest queue times). This may or may not be currently true, since the latest thing added to PvP was for Rival Wings.
- In all of the above PvP modes (except the 1v1 thing), there's never a case where you're "Well, I'm dead, now I can't do anything". Generally, you just wait 5+ seconds and respawn back at the entrance.
- PvP has its own action set! Your PvE skills will not avail you here! There's even a PvP-specific hotbar that you'll have to setup.
- There are a handful of PvP traits/actions that you can choose from and set. Don't forget to do that (though they do have some set by default if you do forget).
- There is a PvP rank and PvP exp, but it no longer serves any functional purpose (it used to limit what PvP gear you could buy, but they got rid of that limitation).