Brilliant! Things you should look to include - though I don't know just what a science fair asks for:
- background information/theory, just to set out the context of what you're doing. It doesn't have to be long
- hypothesis/prediction, which isn't just what you think will happen but why you think it will happen
- results, neatly tabulated
- appropriate graphs, charts or tables of data
- conclusions, which are what you found out and why you think things are the way they are
- evaluation, where you should consider how precise your measurements are, how reliable they are, and so how reliable (trustworthy) your conclusions are. Absolutely do not be afraid to point out the limitations of your experiment; it's a mark of a good scientist and essential for proper investigation
If you believe everything you read, better not read.