Given some text:
Highlight the text to be repeated (one or more words, or whole paragraphs), go to Word's main menu bar and select Insert > Bookmark:
Give the bookmark a name (spaces are not allowed) and click on the Add button:
Note there are other buttons at the bottom what you will be using later as you insert more bookmarks (Delete, Go To and Cancel).
Place the cursor at the point of destination (in this case, the third, blank paragraph) and select Insert > Cross-reference:
A dialog will open. Select Bookmark in the first dropdown menu, highlight the bookmark name in the list and select Bookmark text in the second dropdown menu:
Take a look at the other options in this second dropdown menu, as you may later find some use for them. Now click on the Insert button, then Close and you're done:
The inserted text (officially called a REF field) shows in gray (but it's non-printing) because I have enabled the following option: *Word > Preferences > View > Field shading > Always.*This lets me know it's a Word field (automatic text, if you will).
If you need to edit the original text, it would be better to enable the display of bookmarks (use Word > Preferences > View > Bookmarks), which will then show as non-printing oversize brackets around the bookmarked text. This will ensure that you only type new text where you need to:
Whenever you change the source text, you'll need to update the REF fields. Word does this automatically when you open the document, so you could save the changes, close and reopen the document. However, you can do this manually—select all document content (Edit > Select All or press Cmd A), Right-click (or Control-click) on the text and choose Update field.