The easiest way to create bold lettering is to add Pull compensation. Pull compensation is found on the Sewing Attributes tab of the Integrated Sewing Attributes window. The default location is on the right side of the design window. At the bottom of the Sewing Attributes, click To Expert Mode. If you are already in Expert Mode, you will see To Beginner Mode at the bottom of the window. Pull compensation is toward the bottom. This is best increase in millimeters, not inches as you can increase in smaller increments.
If you are using a TTfont, on the Text attributes tab at the top of the window, under the font pull down menu, there is a tiny arrow. If you click on the Tiny arrow, the options for that font appear. If a bold option is available for that TTfont, it will appear in this location. Choose bold and then click OK. This option only works for TTfonts with bold as a selection.