Making an Oracle 12c Database on Linux
The Tutorial shows you Visually and Step-by-STep How to Create a Database on Oracle 12c by the Database Configuration Assistant on Linux.
Before to Create a Database for Oracle 12c will be Necessary also to Create and Run a Listener.
The Screenshots of the Steps Involved are Inserted here to Make the Lesson Easier and More Pleasant.

First, Create and Run a Listener for Oracle 12c DB
Open a Terminal Window
Login as oracle User
su oracle
Starting the Database Configuration Assistant
cd $ORACLE_HOME/bin
./dbca
If Got Display Not Set or For Any Issue Encountered Look
Select Create Database
Fill In the Database Parameters.
Check the DB Summary…
Click on FinishAfter Wait until the Database is Successfully Created
Then Set the User Admin Accounts Passwords
Finally, Take Note of Database Installation Parameters!
How to Getting-Started Managing by SQLPlus 12c Database