Start the Mail Merge Wizard and then complete Step 1 by selecting the current document as the starting document.
To start the Mail Merge Wizard in Microsoft Word, first click on the "Mailings" tab at the top of the screen. Then, select the option for "Start Mail Merge" and choose "Step by Step Mail Merge Wizard."
In the Mail Merge Wizard pane that appears on the right side of the screen, click on the option for "Use the current document" under Step 1: Select document type. This will set the current document as the starting document for the mail merge process.
Once you have selected the current document as the starting document, you can proceed to Step 2 to select the type of document you want to create (letters, envelopes, labels, etc.) and continue through the remaining steps to complete the mail merge.