If you want to access the IP camera from the internet, then you have to identify which port your webcam uses (most likely port 80, although it could be something else, depends on the URL you use inside your network), then open and forward that port on your router’s firewall. Your router should have an administrative page for this purpose.
Also, since you're probably using a dynamic public IP w/ your ISP, you'll need to use a DDNS (dynamic DNS) service to know your public IP, in case it should change over time. Many routers support DDNS in their firmware. If not, you'll need to use the DDNS client provided by one of the numerous DDNS providers available (DynDNS, NO-IP, etc.).