use the sandbox files:
open
Story_Sandbox_NumberOfPlanetsinGC_FactionName.xml
for example:
Story_Sandbox_56_Rebel.xml(that's a FoC GC)
and then add something like this
<Event Name="Spawn_Han_Solo">
<Event_Type>STORY_TRIGGER</Event_Type>
<Reward_Type>SPAWN_HERO</Reward_Type>
<Reward_Param1>Han_Solo_Team</Reward_Param1>
<Reward_Param2>Hoth</Reward_Param2>
<Prereq>Rebels_Enter_Tech_01</Prereq>
</Event>