Execute the command /regen menu to launch the graphical user interface.
Select "Add More Blocks" (indicated by an icon that is nether star).
Within the Add Menu, two options are available: Global Setting (icon: minecart) and Region Setting (icon: minecart with chest).
For adding the block to global settings, click on Global Setting (minecart icon). For adding the block to region settings, click on Region Setting (minecart with chest icon).