In the "Embed" tab of the "Add" panel on the left side of the editor, in the "Twitter" section, there are templates for embedding

which you can place by dragging and dropping the template of the format you want to use.

To change the content of an embed template to your own, you need to get the embed code first. You can generate the embed code by entering the URL of any content on Twitter with the external service "Twitter Publish".

After copying the generated code, return to the design editor. Open the Detail panel from the <div> at the top left of the code box, paste it into the "Embed code" field, and you're done placing the Twitter content.