To add a new block, move your cursor to the area of your website where you want to insert a new block.
Now click the round + button. You will be taken to the Block Library where you can choose a new block.
Click on the block that fits your website building plans and it will be automatically added to the specified area.
If you aren't happy about the block placement, hover over the block to activate the editing pane. Click on the "cross" Move icon and drag the block to another area.
If you aren't happy about the block design or functionality, simply delete by clicking the "trash" Delete icon and repeat the steps for adding another block.