You can file an international patent application with the national Patent Office or directly to the WIPO (subjected to provision of permission by the state’s national security). Basically, these two offices act as the PCT receiving office.
Initially, you have to file a national application with the national/regional office of your country. Eventually, you will have to apply for an international application and you have to file that with one of the International Patent Offices. That is, patent offices that are eligible to accept international patent applications. Generally, your national patent office will serve this purpose. But, always ensure that your patent office is capable of accepting international applications or not.
The other method to file your application is online directly to WIPO.
Also, do make sure that you check out this free e-book: A Quick Guide to Patents. It deals with basics of patent procedures.
Here you can Download our FREE Help Guides: