Why cant use heroes

I have prophecies factions and nightfall right now i play a d/w carácter and i already unlocked 8 héroes and i want to use with other carácter in prophecies in the same account but i cant use my unlocked héroes anyone knows why? I need to finish the nf camping to use héroes?

You need to get your Prophecies character to Lion's Arch so he can travel to Nightfall. Each character has to unlock the heroes for themselves, it is not account wide.

The heroes are unlocked for PvP use on ANY PVP-ONLY character (Zaishen Mission and Zaishen Elite only IIRC) once you unlock them on on a PVE character, however you will have to unlock them on each PVE character by playing through the campaigns.

For a prophecies character, once you finish the quest Sunspears in Kryta (source- http://wiki.guildwars.com/wiki/Sunspears_in_Kryta), you may unlock Dunkoro, Tahlkora, Koss, and Melonni right outside Kamadan. The rest of the heroes require you to complete the same quests you did on your NF character.