How do I apply for a patent? I want to make a small invention, but I don't have the conditions to do experiments. What should I do?

Doing experiments is not a necessary condition for applying for a patent. It is better to have experiments. Even if not, you can apply for a patent if you can describe the technical scheme clearly. Unless you don't do experiments, you don't even know where there is innovation, and you can't dig out patent points, so you must experiment. But from your statement, it seems that the patent point is already in your mind, and it just needs experimental verification. If so, there is no need to do experiments.