>>How to add the WDT command?

The WDT isn't really a command but a bit you select when you program the PIC. Just like you have to select HS or XS, you get to pick whether to enable or disable the WDT. These are usually selected using menus. Once you get the hang of these, you can add them to your program in this manner http://www.picbasic.co.uk/forum/showthread.php?t=543

good luck