Click on Add Text Box or select a text box in your design.

Make sure your text box is selected (you will be able to view dotted lines and circles).

Under Import Data section click on Start Mail Merge

You can watch a video with instructions by clicking on See How.
Click on the green Browse for File button to select your spreadsheet.
Select your spreadsheet and click on Open.
On Mail Merge dialog box - un-check headers and click on the green Next button.

Drag your Available fields over to the right of the page into the Arrange fields section.

Click on the green Complete Merge button and your information will appear on the labels.