1: How to get a static ip address.
Call up your internet service provider and tell them you wish to purchase a static ip address (some packages come with them. Much home service as of a few years ago charges extra for one).
2: Opening ports
Very simple stuff. You need to assign a static NETWORK ip address to have the router know which ports are forwarded to what computer (google it, very simple settings change). Once the ports are open and you know your network ip (generally 192.168.1.XX or something similar) you can use that for the port forwarding to let people connect to your server.
3: You say you already have a static ip, sounds like you mean external static ip so that's the first step. Just set up the network settings and port forward and you should be good to go.
Warning: Home host servers suck. You're better off just renting a proper server if you plan on having more than like... 10-20 players lol.
