If I have invented something, how can I get it patented and represent it at world level?

As Oliver has basically noted, there is no such thing as a Global or International Patent - patents are territorial for each country. You can effectively get patent approval for a region - for example, if you file a patent application with the European Patent Office - but the ultimate patents will be for countries that you select. Normally, one files a patent application in their own country, and then within one year they file a PCT application - then, within, usually, 30 months from the date of filing of the original country application, you have to select countries or regions where you want to further prosecute applications in order to obtain patents in as many countries as you want or can afford - it can easily become a very expensive process, particularly since many countries charge annuities while the applications are pending or after the patents are granted.