On the Table Tools Layout tab in the Data group click Formula. Just switch to Insert tab and click Equation Insert New Equation to toggle on Equation Tools. Use the Formula dialog box to create your formula.
Step 3 The Formula dialog box by default contains the formula Sum LEFT.
Position the cursor where you want to paste a formula. All functions you can see in the Paste function drop-down list of the Formula dialog box. For some reason the button is not called Calculate. Go to Insert tab find Symbols group and click Equation button.