To insert a callout using the inline editor, place your cursor where you would like it placed, right-click, and choose Insert > Callout. There are a number of alternate callout styles built into the system. You can apply a custom callout style while inserting the callout by selecting the name of the alternate style in the "Custom Class" box. Callouts are designed to start with the H3 class as the highest heading (do not use H1 or H2 tags in your callout).

If you include a H3 element as the first element inside a callout, it will be properly formatted as the callout's title (with the top borders rounded and with no spacing at the top) If you wish to include multiple H3 elements inside a single callout you can fix the rounded corners of subsequent H3 Elements by adding the "no-border-radius" class to them.