When you launch Special Sentences, it displays its main view, showing a list of topics. It comes with five built in topics for you to begin with (these topics cannot be edited). As you add your own topics, these are displayed as well. You can organise your topics into collections: in this case, only the topics in the currently-selected collection are displayed. Chapter 7 explains all about collections.
To start the sentence building activity in a topic, you tap its title or picture. To update an existing topic, you tap its ⓘ button on the right (built in topics don't have this). To create a new topic, you tap the + button at the top.
Tapping the Edit button allows you to rearrange the order of the topics, and delete any you no longer need. You cannot un-delete a topic once you've deleted it.
Please note that you cannot update the built in topics. You can delete them, just like any other topic, if you decide you no longer need them.