On a Palm Device, to install PRC files, simply hotsynch them. They're not applications, despite the PRC extension. For Pleco 1 THEY MUST BE SYNCHED TO INTERNAL MEMORY.
PlecoDict 2 can read these files directly from your external card, so feel free to put them in either internal or external locations.
To install text files, use a card reader (or software which makes your PDA act as one) to put the text files directly onto your SD card.
For Pleco 2, just open the reader to access the files in either format.
For Pleco 1, the PRC files can be accessed easily from within PlecoDict, and there should be a list of those in internal memory. For text files, each time you want to open a file, you must enter the full path to the file.
(Someone please update this for Pleco version 1. For Pleco version 2, just load the files normally.
For all books, the file names and the names that appear on the screen in PlecoDict (for PalmDoc files in internal memory) are all just abbreviations. For whatever reason, the program converting from txt to PalmDoc does not like Unicode, and as such I can't put the Chinese Names in. May require hex editing? But as they're compressed, that's unlikely to work too well…
Also, note that Pleco does not support any Chinese punctuation marks apart from the period (。) at present, so if you don't see any punctuation, that's why.