Once you've added a content block to a page, a toolbar will appear in your site. This is concrete in-context content editor.  You can start typing in content, and use the various menu items to format text, add links (to pages within your website, to external links, or links to PDF files), and add different types of content, such as images, to your content block.

Adding an image to a content block

Click the image icon, then click Browser Server to access the File Manager, where you can find & select an image or upload an image.  Once the image is selected, you can adjust the alignment & other image details, then clic OK to add it to the block.

Adding a link

Highlight the text that you wish to link somewhere, click the link icon, then choose to link to an external link (URL), a page within your site, or a PDF file.  You can also choose to link to an email address by changing the Link Type from URL to email.