In the LAN we all access the server (Centos 7) using ssh but I was wondering how to enable ssh connections from outside the LAN, if a user wanted to use the Internet from their own Network to ssh into our LAN.
What would be the steps needed to make this possible?
As commented need to configure the router to access from outside to any service from any machine on the LAN.
In the router must specify the IP address of the computer on the LAN that are running the SSH service and generally the port on which the service is ejcuta (in this case 22). Depending on the router this is usually in "portforwarding" or "NAT".
On the other hand, on the computer where the service is running you need to keep active duty and accepting requests, this can be seen accessed with systemd service status:
systemctl status sshd
On the other hand you also have to see if the firewall of the computer running the service is active and if so, it is necessary to indicate that supports inbound connections to the SSH service.
This we can manage with the command: firewalld-cmd.
This is usually controlled by your network router. If ssh works on the LAN, then you just need to get into the router and tell it which ports from the outside should be forwarded to which machines and ports on the inside.
