I typically do bottom>top work. Here is the procedure that I use:
1. Create a new project. Open the schematic (you'll be at the 'root' page) and go to File > New. This will be your hierarchical block schematic.
2. Once you're composed the circuitry for the block, leave the nets that go to the ports (pins of the block) dangling.
3. Go to File Save As to save this schematic page as a Cell. In addition to naming the cell, make sure the View is Schematic. Accept the errors/warnings when saving.
4. Add ports to the design and name those nets that leave and hierarchical block. Save again.
5. Go to Tools > Generate View. I accept the default settings, click Generate then Done, and close the schematic page. You're now back at the 'root' schematic page.
6. Using the Component Browser, you can add the hierarchical block from the project's root library like any other component.
7. Once placed, you can manipulate the block by pulling it up with File > Open. The changes will automatically propogate to the 'root' level.
Is that what you're looking for?