The below steps describes how to add user tablespace in oracle.
To add tablespace through SQL, log in (connect to the database using sys as sysdba):
If it is the “USERS” tablespace which is full, a new database file would be named “USERS04.DBF”.
Here is an example that adds a new database file to the “USERS TABLESPACE”:
ALTER TABLESPACE "USERS" ADD DATAFILE 'D:\ORACLE\ORADATA\PROTECT\USERS04.DBF' SIZE 138240K REUSE AUTOEXTEND ON NEXT 10240K MAXSIZE 32767M;
Once the above command is executed successfully then exit the SQL.