You can use the IDE or the command line tools to compile programs for a 64-bit environment.
In the Eclipse IDE, you set your platform target to 64-bit prior to compilation by choosing 64 bit in Platform Target on the COBOL page of your build configuration options.
You can also compile from the command line by using the 64-bit Command Line Tool that is supplied with your product. You use the same compilation syntax as you would to produce 32-bit output; see Compiling from the Command Line (Windows) for more information.
On UNIX platforms, you can control the effective working mode (either 32- or 64-bit) of your environment by using the cobmode utility or the COBMODE environment variable: when the effective working mode is 64-bit (which is the default), the generic cob command compiles a 64-bit executable. You can also use the 64-bit specific compilation command (cob64) from either working mode to compile a 64-bit executable. See The cobmode Utility for more information.