Is this you as an individual or do you represent a company?
If you are an individual trying to patent something, you need to really consider whether or not this is something that you want to do. The process costs thousands of dollars, to start with. And then people think that if you have a patent you have some kind of automatic protection. You don’t. Nothing happens automatically. There are no “patent police”. If someone infringes on your patent, you will not be notified. You have to find out about it on your own. And then you have to take whatever legal action is necessary on your own. If a large company is infringing on your patent, and they find out that you are an individual with limited financial resources, they can take the strategy of basically trying to lawyer you to death. They can file motion after motion and drag out the process, causing you to spend a small fortune in legal fees and such. Maybe they can tie up your patent in court while they file a similar patent that is just different enough to go through the system. Then they profit on their patent while yours becomes worthless. There are all sorts of tricks they can pull to make your life difficult. Can you afford to sue someone in a U.S. court in a process that could take years and require thousands and thousands of dollars in lawyer fees, with no guarantee of success at the end of it? A lot of people can’t. This is one of the reasons some folks say the patent system needs overhauled. It doesn’t work very well for little guys who don’t have a whole lot of money.
That said, even though you might face an uphill battle, it is possible for individuals to successfully defend patents. I’m just warning you that it can be a very difficult and expensive process.
If you still want to get a patent, then you need to contact a lawyer who specializes in this sort of thing. It’s easy enough in the U.S. to find a lawyer with patent experience, and there generally isn’t any risk of them stealing your patent as that would be the end of their career as a lawyer. They will walk you through the paperwork and procedures required. It’s a difficult enough process that you really need someone with experience to lead you through it.
Unfortunately I don’t have a clue about how you would find a lawyer in another country who has experience with U.S. patent law. You may be better off finding a lawyer in the U.S. and working with them long distance.
ETA: The patent lawyer will most likely end up writing most of the text of the patent for you. These things have to be very specific in the way they are worded. There are certain phrases that have accepted meaning through years of being used in patent law. If you don’t use these phrases properly you open yourself up to all sorts of interpretation problems. The lawyer will know how to translate your idea into the proper legal-speak.