Remember that inference is like "reading between the lines". You take information from the text clues in the text and combine it with information you already know (stuff stored in your brain). When you combine these two things together and come up with a logical conclusion, you have made an inference! :)
You can practice inference with pictures. For example: What can you infer from the following picture? Where are these children? What are they doing? How do they feel? How do you know?