sheetcam.com

ok totally new ,, but machine is trucut with offset switch which is set in the mach 3 on the table,, and i suppose i have no clue which post processor i need on the computer to generate g code my table has THC

downloaded my new sheetcam,, when i run post processor it writes the z axis at .375 which is 3/8 off my work how do i correct this , i need the torch to touch down and lift to pierce ht,,, my shop or table computer is running mach 3