First, think of an idea or topic that you want to investigate. you can search it on the internet if you don't know what to choose. then, on a piece of paper, make a title. it is usually in a form of a question depending on the topic you chose. then write your hypothesis or your prediction on what will happen or what will the conclusion be. then do an experiment. you don't have to use expensive materials, instead, use things that are cheap and can be found at your home. as you do the experiment, write your procedures and your observations while doing the process. take down notes. and when the experiment is done, write your final conclusion. you can repeat the experiment if you are not yet satisfied with the conclusion you came up with. and then finalize your report. make your report clear and formal.
i hope this will help you. good luck! :)