how do I get web root on my i phone?

Hello @,
 
Welcome to the Community Forum,
 
 
At this time, there is not an antivirus option available for Apple iOS devices. Because of how Apple manages the apps available in their App Store, there is not a need for one currently. This may change in the future but at this time is is extremly hard/almost impossible to infect an an iPhone/iPad.
 
Webroot does offer two apps you can download from the App Store to backup your files and protect your internet browsing, called SecureWeb and Backup & Sync. You can find either of them by searching for "Webroot" in the App Store on your Apple iOS device. For more information on both of these products please use the information below.
Webroot SecureWeb
https://mobile.webroot.com/brands/webroot/en/help/ios/SecureWeb/index.htm
Webroot Backup & Sync (for SecureAnywhere Complete subscriptions only)
https://mobile.webroot.com/brands/webroot/en/help/ios/SecureSync/index.htm
 
Please look https://itunes.apple.com/us/app/webroot-secureweb-browser/id460986853?mt=8 
 
Also look at this  KB article 
 
If you have any questions then please feel free to ask.
 
Kind Regards.