This tutorial is based on BlueStacks 2.
You can quit BlueStacks by following the steps mentioned below.
1) Right click on the BlueStacks icon in system tray -> Select "Quit"
2) Re-launch BlueStacks.
3) You can also try restarting BlueStacks using the link below.
If you have any further questions, please send email to support at bluestacks dot com.