here we are clonning the database srcdb and creating a new database clonedb

go to database instance and click on create full clone

enter the required details

click on search icon on oracle home. you will get this window. here just put host name and search you see see the the OH and select it

provide password for new database

select the listener

you can select full clone or you can edit parameters if you want

i am editing memory_target from 1744 MB to 1000 MB. click ok

click next

selected the default

click next

review and click clone

monitor the progress

job is suceeded

database is visble in oem

you can verify at database level 

SYS @ clonedb > select name,open_mode from v$database;

NAME      OPEN_MODE
--------- --------------------
CLONEDB   READ WRITE

SYS @ clonedb > SYS @ clonedb > select name from v$datafile;

NAME
--------------------------------------------------------------------------------
/u01/app/oracle/oradata/CLONEDB/datafile/o1_mf_system_hzfoj9b0_.dbf
/u01/app/oracle/oradata/CLONEDB/datafile/o1_mf_sysaux_hzfokm2t_.dbf
/u01/app/oracle/oradata/CLONEDB/datafile/o1_mf_undotbs1_hzfol91j_.dbf
/u01/app/oracle/oradata/CLONEDB/datafile/o1_mf_users_hzfolmym_.dbf
/u01/app/oracle/oradata/CLONEDB/datafile/o1_mf_oggdata_hzfolp9h_.dbf