I want to use an openai assistant in my Unity project, but it must have a file search feature

I want to use an openai assistant in my Unity project, but it must have a file search feature. It should respond with the information it received from the files I uploaded, how do I do this.

You need to build an assistant. They work on a set of instructions. You can feed the instruction and can use a basic prompt like click to execute the instruction. Read API reference for assistant. There are a lot of steps to use an assistant.