Your board works on its own computer. To let people reach it, three things must be true: the board listens on the right port, Windows lets traffic in, and your router passes traffic through to the board.
Telnet at port 23 is the usual way and is on by default. You can add:
Use Network > Services to see them all, with ports, in one list. Two services cannot share a port.
Allow inbound TCP on each port you use. The command and the full port table are on Before you install.
If your computer is behind a home or office router, forward the same ports to this computer's address. The exact steps depend on the router; look for “port forwarding”. Give the computer a fixed address on your network first, or the forward will stop working when it changes.
Callers need an address. Use a fixed address from your provider, or a dynamic DNS name if yours changes. Test from outside your own network (a phone on mobile data is enough).
Boards on the Internet are scanned by bots all day. Two protections are on from the start:
Keep both on. See the section on protecting your board when it is published.
The Connecting callers, Menus and commands and Maintenance sections cover each of these in detail.