alright... Assuming that you have an account that has both Factions and Nightfall linked, take your character to Kaineng Center, talk to Imperial Guardsman Linro and take the quest "Gain Zenmai". You're done, she's the only Factions hero you can obtain.
Btw... Guild Wiki is a wonderful thing. Learn to use it, it will help you a lot.
Also from Guardsman Linro, take the Sunspears in Cantha quest to take your Factions characters to Nightfall. One there, follow the main quests to quickly gain 6 or 7 NF heroes.