I'm from Colombia and wanna go to China for 3 or 4 weeks. what should I do?

Orlando, where you are you now? If you are in New Zealand, you need to apply from Chinese consulate in your area. By the way, what's you purpose of visiting China? There are several kinds and you should apply one according to your purpose. If you just go to China for a trip, then a L type is OK. You need to provide round-trip air tickets, hotel reservation in mainland China and a copy of your resident permit for employment apart from your passport, application form and a recent passport photo.