When you're done, you can click on the 'Close' tab on the floating bar. The items in the header and footer will appear greyed out, but don't worry; this only means the they have been set. The cursor will then appear on the first line where you can begin typing your letter.
If you look around, you'll notice that everything is labeled. From a small jar to a large office desk, each and every item is bound to have at least one label. Labeling things is useful, easy and practical, and the applications are virtually endless. You can find a wide variety of labels available on the market, in different shapes and sizes, styles, designs, colors, materials, templates and so on.