It's pretty easy - you just need to ensure the GSM module has a good power supply, and that you know your mobile carrier's access point details (it's easy enough to google).
If you've got other questions it might be better to post up in a new thread though - this one's getting a bit long!
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
Yes, absolutely! There's a page with some information on how to do it here: http://www.espruino.com/SIM900
It's pretty easy - you just need to ensure the GSM module has a good power supply, and that you know your mobile carrier's access point details (it's easy enough to google).
If you've got other questions it might be better to post up in a new thread though - this one's getting a bit long!