Welcome to Smogon! Take a moment to read the Introduction to Smogon for a run-down on everything Smogon, and make sure you take some time to read the global rules.
No problem. Do you know your timezone? GMT means Greenwich Mean Time. When I say that I'm GMT -7, it means that I'm 7 hours behind GMT +0, which is London. If you live in the USA, Canada, or Latin America, you'll have a timezone between GMT -4 and -8.