I did some Palm work some time ago; you have to go to their website and sign up for their developer program. Then you get some software which lets you emulate a Palm III or Palm VII.
All the docs you need are right there. Basically you end up making really tiny HTML pages with really simple Black & White graphics.
I don't know if they've changed their policy but when I was doing Palm work, before you can get the development software you have to sign this contract and mail it to them. Real pain. To top it off their website was the most buggy convoluting thing I've ever used. But their emulator worked great.