Starting from the bottom of the barrel.

[GrumbleBeard]

You gain pvp points as you rank up. You rank up by pvping. You're correct that frontlines is your best bet to learn, try asking around to learn the prime times to queue for your data center.
As for your abilities, you can use all of them even without allocating points into them. Take the time to read the tooltips for them, usually they are pretty valuable abilities.
The rest is just practice, play around and do your best, learn from mistakes and try to have fun.
You can go to Wolves Den Pier and use the pvp only abilities on the training dummies on top of the boat to get an idea on what they do.

[Ninster]

As for your abilities, you can use all of them even without allocating points into them. Take the time to read the tooltips for them, usually they are pretty valuable abilities.
You can go to Wolves Den Pier and use the pvp only abilities on the training dummies on top of the boat to get an idea on what they do.

I completely missed this, and now I'm feeling a bit less helpless now. I think I'll spend some time at Wolves' Den then. Thanks!

[Februs]

You can go to Wolves Den Pier and use the pvp only abilities on the training dummies on top of the boat to get an idea on what they do.

All good advice, but I highly recommend this last bit.

The number one thing that people have trouble with in PvP is wrapping their heads around just how different it plays from PvE. For a Dps, you're primary concern is not longer achieving max damage over the entire duration of the match. Instead, it's scoring kills. At first that might sound the same, but it's really not. You have to focus on your strongest burst possible in the shortest amount of time possible. Not only will that change your rotation, but with the inclusion of PvP skills you'll have to get accustomed to an entire new hot bar set up. It can really muck you up when you first get into it, so the more practice you can get in with it the better.

Another thing to keep in mind is your strengths and weaknesses. Unlike PvE, you're playing against opponents who are not bound to enmity tables. Be aware of that when you get into the arena and use whatever you can to keep yourself alive. You specified Smn and Brd (I feel sorry for your queues lol), both of which have exceptional stopping power at range. Use that to your advantage, be aware of your surroundings, and keep moving. Proper positioning can play a big part in how well you can survive.