While Microsoft Word is not the ideal software for designing postcards, you can still create a postcard design by following these steps:

• Set the page size: Click on the "Layout" tab in the top ribbon and choose "Size" from the drop-down menu. Select the appropriate postcard size from the list of options, or you can create a custom page size.
• Add an image: Click on the "Insert" tab in the top ribbon and choose "Pictures" from the drop-down menu. Select an image from your computer and insert it into the document.
• Add text: Click the "Insert" tab again and choose "Text Box" from the drop-down menu. Draw a text box on the postcard and type in your message. You can also change the font, size, and color of the text using the options in the top ribbon.
• Add design elements : You can add design elements such as shapes, lines, and borders to your postcard by clicking on the "Insert" tab and choosing "Shapes" from the drop-down menu. Choose a shape and draw it on the postcard.
• Print your postcard : Once your postcard design is complete, print it out on thick paper or cardstock. If you have access to a printer that can print double-sided, you can print the address and message on the back of the postcard.

While Word can be used for basic postcard design, it does have its limitations and may not offer the same level of flexibility and creativity as other design software. If you need more advanced design features, consider using dedicated design software such as Adobe Illustrator or Canva.

Or more ideally, contact freelance postcard design services for professional consultation. With deep knowledge of design and experience in the field, they will make sure your postcard fully delivers your spirit and own style in the most effective way possible. Not to mention, freelance services often give you more options to choose from available templates online and offer you a very reasonable price compare to others.