To present the software in the Palm Pilot emulator, an entire operating system for the device is loaded in. This means it's possible to leave the program being emulated entirely, interact with the operating system, and return. The entire emulator expects a mouse or touch-screen interface for interacting with it - all buttons and click/touchable areas should "just work".
There is a symbol to the left of the writing area underneath the House/Home icon, which drops down a menu; many times the programs will make more sense if you drop down the menu and see additional options. In the writing rectangle is the famed Palm Pilot writing system, which uses strokes of a finger or pen to add text. This writing system, "Grafitti", is complicated but can be found by searching for Palm Pilot manuals.