What passage this is very unclear
The answer is: figure out meaning based on what you already know and what the text says
To infer something from the passage, you need to read it and able to understand the meaning of the passage without actually put too much focus on the passage.
Passage inference could be considered as a reading skills. This usually tested when you do an SAT test to measure how much information you can gather from reading a certain text within a short period of time.
