The typical workflow consists in sending whatever interesting stuff you may find to the Inbox: be it in an email, on a web page, or in an application. The idea is to allow you to store information quickly, in a non-intrusive way, and to organize things whenever you want.
The system clipboard can be sent to the Inbox using the Action menu, or the correspondent keyboard shortcut. You can also store the clipboard directly in a folder, by selecting the folder and clicking on "Store clipboard here".
The selected content in the current application can be sent to the Inbox using the Action menu, or the correspondent keyboard shortcut. The selection can contain text, images, or a mix of both.
You can for example select a portion of web page: all the information (text, formatting, links, images, etc. is stored).
When you need to quickly jot down some thoughts, you can create a text note (from the Action menu or using the correspondent keyboard shortcut). You can type a title and some text. To confirm, click on the "Ok" button or press ⌘-return.