How do I file for a divorce?

I've been separated for 5 yrs., have 3 children now 12, 18, & soon to be 20. They keep in touch w/their dad by phone. When he's asked where he lives, he claims he's homeless and lives in a tent. He also tells them he only works cash money here & there. I ended our relationship because of domestic issues & till this day I still do not feel safe telling him where I live for fear of coming home & seeing him at my front door. Does anyone know how long it would take for me to get a divorce if I do not know his whereabouts?