First, create a custom user field userRealName in profile details as a Single-line text box to grab your user's real name (whether first or last). This will help customize the shareable message to personalize it for the receiver.
And, upload invite.png (attached) to your home directory, or wherever you keep images. If you change directories, ensure the <img> tag reflects the new image path.
Then, create the HTML widget.
For the widget template, use this code...