You should have at least two columns of numbers that will be representing your Input Y Range and your Input X Range. Input Y represents the dependent variable while Input X is your independent variable. If your version of Excel displays the ribbon, go to Data, find the Analysis section, hit Data Analysis, and choose Regression from the list of tools. If your version of Excel displays the traditional toolbar, go to Tools > Data Analysis and choose Regression from the list of tools. In the Regression Analysis box, click inside the Input Y Range box. Then, click and drag your cursor in the Input Y Range field to select all the numbers you want to analyze. You will see a formula that has been entered into the Input Y Range spot.  Choose whether or not to display labels, residuals, residual plots, etc. by checking the desired boxes. You can either select a particular output range or send the data to a new workbook or worksheet. The summary of your regression output will appear where designated.
Enter the data into the spreadsheet that you are evaluating. Open the Regression Analysis tool. Define your Input Y Range. Repeat the previous step for the Input X Range. Modify your settings if desired. Designate where the output will appear. Click OK.