Highlight the words. Open the Text Properties Box by pressing CTRL and E (or CMD and E on a MAC). (My files will not work on phones or tablets; only on computers.)
Click the "More..." button at the far right of the Text Properties box. This will open a new box with advanced settings. Click on the "Paragraph" tab at the top to choose alignment and spacing options.
Depending on how it looks, you may want to move the words a little more to get them perfectly centered (since sometimes the text is little lower than it should be).
** All editable files are for PERSONAL USE only.
Read my other editable tutorials for more tips and tricks for editing your files.