Your completed kernel is the file bsd in the compile directory. Before you use your new kernel, verify that you have your current, working, well-behaved kernel backed up to a separate file on the root filesystem, and then copy your new kernel to /bsd. That’s it! The next time you reboot, you’ll come up on your new kernel.
Some people do not like to copy their custom kernel to /bsd until they’re certain that the kernel will boot. If you’re one of these people, copy your new kernel to the root directory under a different name, such as /bsd.test. Boot into this alternate kernel. Test your system. If everything works, properly install your new kernel.