Within a pane, click/tap on the appropriate icon to add text, an image, or a module.
You can move the module to a different pane in the current page.
You can hover over the empty area of the action menu bar of the module until the cursor changes to a four-arrow cursor, then drag the module to a different pane.
You can click/tap on the four-arrow icon to expand the Move action menu, which contains the list of panes on the page. Then choose the target pane.