Download & Install putty

https://www.putty.org/

Putty Configuration

Connection > SSH > Tunnels 

Check [Local ports ....]

Check [Remote ports ....]

Source Port : 15219

Destination : yourdb.server.com:1521

Click [Add]

Do not click Open button, You must save this configure...

Session :

Input your Host, ssh Port, Saved Session name, and Click [Save]

Putty Open & Enter password

Toad Session Connection 

localhost:15219