Fill light must always be lower. It's to lighten shadows, not create new ones. But I never use fill-in with a softbox, if it's soft enough - just a reflector.
Start with the key light above the model's eye line and just to one side.
If you're starting out, use only one light and try a few variations with that. Multiple lights are much harder to use and just add confusion until you know what you're doing. You don't need a hair light unless it's dark hair against a dark background, or at least it's not essential.
Build one step at a time and don't add extra lights until you've nailed the first one.