Could you guys help me with the start of a story pwease? :)

So, I have this really good idea for story but I have no idea how to start it! D: I'll try to give you the gist of it.

Okay, it's a relatively modern setting but, there's still slave markets. The main character is a girl (I haven't got any names either so if you could help with that too it'd be great) The girl and her brother are slaves to this family who live in a small town. There's this big city miles and miles away from their town where this guy she's in amor with lives (I haven't figured out how they met...) and every so often portals to the city open up in aleatório places that only certain people can use, the main character being one of them. Anyway, whenever she can find a portal she sneaks out to the city, with the help of her brother, to meet the guy she loves.

Anyway that's the gist of things, I've got a bunch of complications planned for it and stuffs but if you could just help me with the start that'd be great! Even composição literária this has set off a bunch of ideas!
Thanking you all in advance! :)