Hello, Hùan! Welcome to SOTE! Glad you could find this place and hope your enjoy your stay :D
SOTE is a pretty open world, so as long as your ideas don't break canon for what is pre-existed, you can pretty much do your own thing. If you're stil uncertain, you can always assume your area might exist outside of the main SOTE continent that's currently created, as it is presumed there IS more to the world than the main world posted, which makes it pretty awesome so you can sort of imagine what you will if you don't see one of the current nations fullfilling your character location needs :)
If I'm mistaken, I'm sure Rhi will correct me, but I've done that myself and listed the details in my character's profiles (for those who are from areas outside the main land). If you want to make something more extensive and have others participate in such a location, you most certainly can, and can always get started by posting something in the plotting board
here.
And your questions can always be posted
here, where they will (eventually) be seen by another member or mod who can assist you.
Hope that helps and happy rping!
-the spice