Please help me to upgrade my Macbook pro Retina 13 inch Mid 2014. Its system is Yosemite 10.10.5. It's not compatible to many applications.
How to upgrade MacOS High Sierra? I have the Apple ID but I can't sign in Itunes and App Stores. It's advised that my Apple ID or password is not correct although I have keyed in the correct one.
MacBook Pro 13″, OS X 10.10
