In the top left part of the window click the Preferences button
In the Preferences window go to the Virus Scan tab
In the left part of the window select the Full Scan section
In the right part of the window set the necessary security level by scrolling the slider:
Maximum protection. We recommend using this level if you suspect that a virus has infected your computer.
Recommended is the optimal security level as it rationally uses system resources and provides secure protection. This security level suits most of the cases.
Maximum speed. This level should be set only if you are sure that infection is not likely. While the security level is decreased, additional system resources become available.
Close the Preferences window and the main application window.
You can create the Custom security settings by customizing the protection settings. You are advised to select as a basis the level closest to your requirements, and edit its settings during the full scan task.