To answer your question, in order to apply for a Green Card for your wife you must be either a US Citizen or Green Card holder. Assuming that you are, then once you get married you can submit a petition for your wife. However, please note that the process usually takes 6-12 months to complete.
Alternatively, if you are a US Citizen, you can apply for a fiance visa for your wife (which usually takes less than 6 months). If you are approved for this visa, then you and your wife can enter the US and you must get married within 90 days of your entrance. You can then remain in the US while your wife applies for a Green Card.
If you do not use the fiance visa or the marriage visa, then your girlfriend/fiance/wife will need to find a separate visa pathway to enter the US (e.g. job offer from a US employer in a high skilled profession).