If you haven’t installed 12C ORACLE_HOME, then below the below link.
Install oracle database 12c software
Once installation is done, Let’s create one container database(CDB) with 2 pluggable database (PDBs).
$ORACLE_HOME/bin/dbca
Here we will create one container database with 2 Pluggeble databases.
Configure Enterprise manager
With this your multitenant database creation is done.