To get to the PvP isles, you'll need to be able to access the boat at the major port city in each expansion: Lion's Arch, Kaineng Center and Kamadan (though you need to be able to get off the starter island in order to access the boat I think. May be wrong there, it's been a while.)
From there you can go to the PvP isles. When you get to the PvP Isles, you can't go straight to HA.
To get to Heroes' Ascent, start in the Random Arenas. Win there 5 times in a row, to unlock Team Arenas. Then win in the Team Arenas 5 times (it doesn't have to be in a row), which will unlock Heroes' Ascent. Source - Wiki (
http://wiki.guildwars.com/wiki/Heroes%27_Ascent)
However, as you say you're new, I *strongly* recommend taking a PvP character into PvP as you can customise it with everything you've unlocked, rather than what you currently have on your character.
Before the event starts I recommend getting yourself familiar with the PvP isles, PvP creation and things like that. A lot of good info can be found in the wiki page I linked up there, and the page about the Battle Isles itself at
http://wiki.guildwars.com/wiki/The_Battle_Isles
As a newbie to these areas you probably wont have the best of luck this weekend, but wish you all the best all the same
