Speak with "Lionguard Figo" in "Lion's Arch". He will give you the quest "Sunspears in Kryta". Completion of this quest will gain you Travel to Kamadan.
If you also have Factions, I'd suggest going to Factions first (no fighting quest), and going from there to Nightfall. Prophecies to Nightfall: 6 people party, low lvl hench. Factions to Nightfall: 8 people party, lvl20 hench.
true, quest from LA to Kamadan way harder than from Kaineng
if you have to go from LA, consider bringing a friend with heroes, the quest done henchway is quite a pain
