How do I fill all address boxes in label template with same information?

Did you select just the cell content, or did you select the entire cell, including the end-of-cell marker?

Since your screen shot shows that the template does not contain any fancy graphics, it would be a lot easier for you to use the built-in label definition in Word.

1. On the Mailings tab, in the Create group, click Labels.
2. In the Envelopes and Labels dialog (Labels tab), click Options...
3. In the Label Options dialog, for "Label vendor," select "Avery US Letter."
4. In the "Product number" box, scroll down to 5520. Note that the numbers are sorted alphabetically rather than numerically, so you have to go down past all the 1s (even five-digit ones), 2s, 3s, and 4s to get to the 5s.
5. Click OK to select the 5520 label.
6. Back in the Envelopes and Labels dialog, type the text you want on the labels. If you want to change the formatting, you can select the text and right-click to get Font... and Paragraph...
7. Select the radio button for "Full page of the same label."
8. Click New Document. You'll get a sheet of labels which you can then further edit as needed.
9. Since you want different content in each column, however, you don't really want a full page of the same label, and the copy/paste technique we have described should work for you provided you select the entire cell before copying. If I copy just the text without the end-of-cell marker, I do get the same results as you.