After installing drbdX-utils, install module.  Then depmod -a.
Then configure disks by editing /etc/drbd.conf.
On each server:

     drbdadm create-md r0
     drbdadm attach r0
     drbdadm syncer r0
     drbdadm connect r0

Then on one side:

     drbdadm -- --overwrite-data-of-peer primary r0

Wait to synchronise.