Detailed Chart Tutorial?

I am able to create charts in Excel but totally missing out on labels and categories.

For example I am create a chart of # of calls for a support center. I have a row of cells for each user where each cell is the number of calls per day. I select the data and create a chart without any problems but do not understand labels and catagories.

Anyone know of a good tutorial that will cover every keyclick for creating a chart with labels?