Click on your Avatar (top-right corner), then click on Settings.

Select the Structures tab, then select the structure in question.

Next, click on the Customize Frames button.

In the sidebar you will see all the elements for this structure. For this example we will modify Thesis. Go ahead and click it.

From the options select Help Cards.

You will how see the cards that are available while writing. Change the text/content and the system will autosave.
​Note: you may add an extra card my pressing the + button.