On the Basel theme, you can not add the image or link. However, don’t worry about it.
Just do as these steps:
Step 1: Go to Page -> Create a new page -> Choose the template with: page.about_us and write the content
Step 2: Show the content on the page
+ Copy this text: text>testimonials>member>page_content then paste to the box:
+ Then you’ll see all the content shown on the Page
Thank for reading!