which version of OBIEE are you trying to install? is it 18.104.22.168.6? Did you use SYS or SYSDBA user/role in the RCU DB details screen? if not then you wont be able to create those schemas
OBIEE support Oracle DB 12c, you can check in the certification matrix for the details (google for the matrix).
For a certified system you will need to upgrade weblogic, if it's just for testing or a certified system isn't required you can also use it directly.
In case your 12c is setup as multitenant you need to specify a connection to a PDB and not the CDB (but still using a SYS / SYSDBA account) in the RCI.