Go into the Pokemon center, talk to the girl next to the globe. Click on GTS, Then on GTS again, next go with the first option and you will be asked to save. After that you'll be asked if you want to connect to wifi, hit the first option. Now your in GTS, the first option is for you to trade a Pokemon you have, the second option is to look for Pokemon that have been put on GTS for trade. The last one is to exit out. The rest is pretty simple from there.
"Don't walk behind me; I may not lead. Don't walk in front of me; I may not follow. Just walk beside me and be my friend."