You need to connect to the Reporting Services instance, not the SQL Server instance that contains the ReportServer db.
If you go to the Object Explorer and click Connect you'll see a dropdown showing the different types of instance you can connect to. Click the Reporting Services one.
In the connection you can either use the instance name or the address of the reporting service ( e.g. http://localhost/ReportServer ). Once you have this open in object explorer right click and view the properties, it's under here that you will find the logging options.
Errors in BIDS are not logged to the Execution Log since BIDS renders the reports independently of the Reporting Services instance.