You have 3 options.

Have a domain set up and use reverse http/https payload which is better than the tcp version. That way even if you use a diffrent network(public ip) the payload can still get back to you. Cheaper than ngrok.
Ngrok free version has limited time for a connection. The link changes each time a fresh connection is started. It's good for testing but what if you want to use the keylogger for an extended period of time? Paid version is about 18 usd if you don't find if a want of money.
Port forwarding id done in the router config panel. differs for each model but the key words the look for are port forwarding/triggering. Am sure somebody has made a blog/vlog that you can use. However this setup does not support mobility.

How to port forward? #829

Description