As per the screenshot which you had shared, you had not provided the RULES and DATA schema names in "Rules Schema Name" and "Data Schema Name" fields. Please enter the RULES and DATA schema names in these 2 fields, then try the Test Connection.
Also in your URL jdbc:oracle:thin:@localhost:1521:dbName -> you can try this format and replace dbName with your database name where you created your schemas.
Hope this changes will fix your issue, if not share me the latest issue after applying this changes.
I would like to know whether you are installing the personal edition or standard edition of Pega 7.3.1?
If you are trying to install personal edition then the installation process is different as explained over here.
If you are trying to install the standard edition with the Single/Split schema concept you can look for the reference document over here. You can refer the specific document based on your Database and Application Server.
Hope this might help you to understand the installation process.