Documentation about CY... constants and APIs you'll find in the System Reference Guide which is acessable from the Help-menu in Creator.
On the other hand, a pin may be defined as input and output and additionally this can be controlled with an output enable (oe) signal, see at the Pins-datasheet.
If you go to Architecture TRM there is a section on I/O, a summary of the registers you
can write to control pin parameters.
There is a Register TRM that has indepth details of the control registers and
This ap note should help as well -
http://www.cypress.com/?rID=57571 AN72382 - Using PSoC® 3 and PSoC 5LP GPIO Pins