A quick summary is as follows:
- Welcome, a nice welcome message
- Open, an active label to open existing capture files
- A list of previously opened capture files
- Capture, an active label to open the capture dialog
- Capture filter entry, an text box to enter the optional capture filter
- A list of detected capture interfaces, either network or otherwise, with their current activity
- A few links to information resources
- Version information
Probably the first things you want to do is either capture some network traffic, by clicking an active network interface, or opening an existing capture file. And then go from there.
The documentation is in the works, so the User's Guide is set to improve, also on this point.