Before you can use the Mach microkernel in your system you'll need to install it and all components you want to use with it, e.g. the rest of the operating system. You also need a bootloader to load the kernel from the storage medium and run it when the computer is started.
GNU Mach is only available for Intel i386-compatible architectures (such as the Pentium) currently. If you have a different architecture and want to run the GNU Mach microkernel, you will need to port the kernel and all other software of the system to your machine's architecture. Porting is an involved process which requires considerable programming skills, and it is not recommended for the faint-of-heart. If you have the talent and desire to do a port, contact firstname.lastname@example.org in order to coordinate the effort.