Turn on my iphone icloud

This document tells you how to sign into iCloud --> Sign in to iCloud on all your devices - Apple Support

You can then configure it to use the features you wish to use:

Change your iCloud settings - Apple Support

Is your apple id disabled in the App Store and iTunes?

Then there is something wrong with your account that cannot be solved at your end. Please Contact - Official Apple Support for further assistance at a time they're open.