How do I delete, log-off,or block off an iPhone se/7 from using my iCloud account

How do I get rid of these devices that are all logged in and are using my iCloud account on their devices. And, they switched from my original settings to their settings. They see and read all everything I do. It’s like my phone is there’ and there is mine. My iPhone 11 is being controlled by a iPhone 7 and Mac something