This assumes your port 1521 is not open.First you need to Load the putty session you saved in previous case(to enable SSH access).In the Category tree, click Tunnels. The Tunnels panel is displayed.
In the Source Port box, enter the number of an available port on your system. Specify a port number greater than 1023 and less than 49152 to avoid conflicts with ports that are reserved for the system. As a good practice, and for the sake of simplicity, you should specify the same port number as the one to which you are creating a tunnel.In the Destination box, enter the IP address of the target compute node, a colon, and the port number to which you want to create a tunnel; for example, 220.127.116.11:1521.
Please note the SID and SERVICE_NAME which will be required to connect to database
Open sql developer and provide below input to connect to PDB.
Please open SQL Developer and create new connection with following entry.Please use password provided during instance creation.Then Test connection.It should show status:Success
Now if you do not enable SSH Tunneling, you will get below error when you connect database using public ip