learning excel - Data point bar labels

I am using Excel. Each chart is sourced to one column of data. The data is numerical values. The Excel spreadsheet has eight column headings each of which are a different test number and the perfomance values plotted are of the same format under each test number. I have a seperate chart for each test number, with all staff represented on each plot. The rows in the spreadsheet correspond to the relevent staff initials. The first column of the spreadsheet is used to show the staff initials. Only the data values are a source to the plots currently. I have tralled through every single available option on every tab that relates to formatting, with much effort concentrated on anything that might be to do with labels, I've tried them all out to see what they all do but this did not tell me how to label each plot with the staff initials. I very much appreciate you trying to help.