From the Theme Editor, click the arrow before the section name to open the list of blocks.
From this list, click a block you want to edit its settings.
From the list of blocks, click on a block you want to remove. You will see the Remove button on the bottom. Just click this button to remove the block.
Click the Add block button below the list of blocks to add new a block.
Move the mouse the to block you want to rearrange, use the left mouse to press and hold the last icon, then move the block to a new position you want.
Move the mouse the to block you want to show/hide, click the eye icon to show/hide the block.