Your computer will have the ability to pull new security updates from Microsoft once it has Service Pack 1 installed. You can set them to download and install automatically (which Microsoft recommends) or let Windows give you a notification that an update is ready to download. You should consider following the Defrag C: instructions periodically.
You need to decide how often you want your computer to be backed up, and to where. Some people add backups to an external hard drive, a USB drive, a network drive, or to the cloud.
Good security software is constantly on the lookout for new threats. Definitions are typically updated automatically when your computer is connected to the Internet, but you should verify they're being downloaded and updated.