Watch Dog Timer Commands MSP-430 Processors

Hardware wise, there are a few different WDT variants for different MSP430 chips. You can find out which variant of WDT is used in each MSP430 chip in the Data-sheet of the chip.
Software wise, one can use #define to do all kinds of thing. When in doubt, try to find the definition used.

Thank you.

The WDT of the MSP430 is controlled by a hardware register, which is memory-mapped (like almost all other MSP430 features except the low power mode controls and the global interrupt enable, which reside in the processor status register).
The register is password protected. Its description and the meaning of all of its bits is found in the family users guide that belongs to your MSP. (there are some differences between the different MSP families, even though the general functionality is the same for all)
The header files of all compilers define the watchdog register as a global symbol, so you can access ti like a variable. Also, the password, the individual bits and even some common bit combinations are available as defines.
Normally, you don't need to define anything on your own.
The register name as well as the bit names should match the names used in the users guide. For the pre-defined combinations, you will need to take a look into the header file.