Provided your DRBD build completed successfully, you will be able to install DRBD by issuing these commands:

cd /usr/src/drbd-x.y.z
make install

The DRBD userspace management tools (drbdadm, drbdsetup, and drbdmeta) will now be installed in /sbin.

Note that any kernel upgrade will require you to rebuild and reinstall the DRBD kernel module to match the new kernel. The DRBD userspace tools, in contrast, need only be rebuilt and reinstalled when upgrading to a new DRBD version. If at any time you upgrade to a new kernel and new DRBD version, you will need to upgrade both components.