Hmmm... strange I thought there would be lots of copies of the manuals around by now.
Oh well. Chess was written for the TI99/4 and used keys appropriate to that keyboard. The docs were immensely thick but mostly tried to teach you to play chess - there are lots of web resources teaching you to play chess.
For the TI99/4a the short cut keys were a kludge and made little sense. The manual relevant to the TI module was reduced in the European multi-language manual to a mere two pages, and some bits (eg setting up a problem) were omitted (choose "If you wish to practice"). Follow the on screen menu choices and you will probably get it, as that is what TI left you with.
So here they are.