A block is added to the active schematic by dragging the block from the blocks tree to the schematic with the mouse. The blocks tree is opened by clicking the Blocks tab in the tree view. Read more about the blocks tree in the The Blocks Tree section.
A block can also be added by right-clicking the block in the blocks tree and selecting Add to Schematic in the context menu that appears, or by selecting the block in the blocks tree and pressing the Enter key.
When the new block instance is added, it will be given an instance name that is unique in the schematic. The instance name will be the block name with a number appended on it. For standard and user blocks, the name is displayed with green text above the block instance, and it can be changed as described in the Renaming an Element section.
In RTflow, it is not possible to drag empty blocks from the blocks tree into the schematic, as is possible in some similar software. Instead, create a new schematic, add ports to that schematic and compile it. Then the new block will be available in the blocks tree.