If you wish to view the IP camera over the internet is a bit more complicated than viewing from the same wireless network,
http://www.tp-link.us/faq-304.html, gives an idea of the setting you will need to make to your router,
The WAN ip address will be the stumbling bloc, you will either need a "static" address so your routers Internet address doesn't change or use a DDNS service (again your router needs to support this) to keep track of the latest IP address your router is assigned, there are a number of "free" DDNS services so not adding to cost just complexity.
you will find that unless you have specifically asked for a Static address (and possibly pay extra per month) you routers internet IP address will change on a regular basis,
its also a good practice to "reserve" the internal IP address allocated by the router to the IP camera as you will be using that to "port forward" to.
Gary