Okay, someone walk me through Microsoft Excel, please ...?

I want to make a chart in Excel that will plot weight loss and things like that. I can get the chart on the sheet, no problem, but I can't seem to figure out how to edit the chart so that it shows my data, let alone being able to figure out how actually plot my data. Can anyone help? I am a total beginner, so I need something simple and straightforward, and if you know of a web tutorial that is free that would be awesome! Thanks ...