Noob question on chapters and characters

I've done a forum search, looked at the stickies, and looked at other sites to find answers, but I haven't found one answer that I was hoping someone could explain to me. I understand to create a certain character you will have to make it in the chapter that they are exclusive to and you can play that character in the other chapters. I do believe my accounts are linked, but how do I go about playing an assassin in nightfall or dervish in factions? Do I have to physically travel there, is there something I can do during character creation/select, or do I have to play through their respective chapters first?

First of all, you would need the campaigns on the same account, obviously.

Secondly, as soon as you get up to a certain point (Kaineng Center in Factions, Lions Arch in Prophecies and Consulate Docks in Nightfall), you will be able to enter several quests to travel in between the continents.

Extra info here, along with quest names etcetera.

Thanks for the info Haxor, this did answer my question. Are these quests part of the primary missions? If I use the same username and password to play each campaign then they are, in fact, on the same account? Just want to make sure.

The quests are not part of a primary mission. Also, if you log in with a certain password/email combination and can then choose out of all three the campaigns to make a character in, they're on the same account.

Haxor is only partly right there, though. As soon as you get the quests, you'll also start a primary quest on the other continents.
So, if you have a character from Prophecies, get the quest to go to Factions and travel there, you'll have 2 primaries; one in Tyria (Prophecies) and one in Cantha (Factions).

=).

If you use only one username and password to login to GW, then they must be all on the one account.
When you start a new "core" character, you can start in any campaign you have. The "look" of the character - the available choices of face, hair style, etc. - will be different in each campaign, so you might want to try each one to find the look you want. The core characters are the original 6 - Ranger, Warrior, Mesmer, Monk, Elementalist, & Necrmancer.
If you want to play an Assassin or Ritualist, you must start the character in Factions. If you want to start a Dervish or Paragon, you have to start them in Nightfall.
Once any character gets to the particular cities as mentioned above (L.A., Kaineng Center, Kamadan), then you can do a small quest(s) to enable them to travel to the other campaigns. Once you've done the quests, you can simple "map travel", using the boat, to go back and forth between campaigns, at will. (You are not stuck in the other campaign.)

P.s. It sounds as though you are using different "links" to start GW in each campaign. Actually, if they are all linked to the same account, you only need one link. All the characters from all campaigns will be available from the character select screen.