Create new block by pressing <righ-click> on empty place and choose block.

Edit block by pressing <right-click> on top of a block.

Create new link by pressing <left-click> on input/output port and then on output/input port.

Delete link by double clicking on existing link.

Warning: You can't calculate if there is no display block.

Warning: Input port doesn't have input port you have to set it in menu.