Emoji is very popular in messages or chatting apps, but it does not come automatically with Microsoft Word. If you only insert a happy (sad, neutral) face, please check how to insert a happy (sad, neutral) face. If you want to add the full set of the emoji, please see the steps below:
Step 1: Click the "Insert" tab from the ribbon;
Step 2: Click "Get Add-ins" from the "Add-ins" section (if you have an earlier version, please click "Store");
Step 3: Type "Emoji" in the search box and the Emoji Add-ins package appears;
Step 4: Click "Add" to add the Emoji set. After you will find the Emoji command from the "Insert" tab;
Step 5: Click on "Emoji keyboard", all the Emoji will appear in a new window.