Computer on your Local Network can access your computer

That statement is intended to impart the NAME your computer presents to the Network, nothing more.

Rest assured that unless you allow some services, nothing is currently being made available on the Network at that name except the existence of your computer and the name shown. No shared files, no shared Printers, no remote login, nothing.

Even if you were to authorize some of those services, almost all require a separate login with a UserName and password valid on YOUR computer (not just the remote computer). MacOS is inherently a Multiple User System, and services and files are protected from all other users, local and remote.

There is no security risk here. What that means is that, if you were on a LAN and there was another computer you wanted to connect to, that is the address they use. It would still require you and the other person to allow the share to actually take place.

When you use your Internet-connected computer from behind a Router you control, the standard setup provides Network Address Translation. This means you local Internet address is from a range IP address that is strictly private, and not reachable from the Internet.

The Router acts as your agent, sending requests to the Internet on your behalf. Only the responses to your specific queries are returned to your computer. All other packets are discarded. This makes your computer nearly invisible -- only your Router can be seen, and its has nothing to say for itself, so it accepts nothing for itself.

That doesn't matter. It is simply a statement of potential. Again:

If you were on a LAN and there was another computer you wanted to connect to, that is the address they use. It would still require you and the other person to allow the share to actually take place.

The key word is If. As you're not, it's all irrelevant and can be ignored in complete confidence.