Ahoy-hoy!

Up there is a heading block. This is a text block. Click on a block to select it.
Double click either of them to start editing the text.

On the left there is a list of block types. Clicking will insert a block before the selected block. Sorry you can't yet drag a block from the palette to the page. You can drag blocks about on the page though - drag the grabber on the left of the toolbar immediately above (or below) the selected block.

Have an experiment with the containers - Row and Stack and see how they work. You can move blocks between containers.

Click on the floppy disc icon to save your changes.