Issues Updating OS system after factory reset

I factory reset my MacBook (early 2015 model) and it has reinstalled Yosemite. I want to get it back to High Sierra but I'm really struggling. It won't connect to the internet properly (white bar comes up), so I airdropped the High Sierra link page in the App Store to the old Mac from my new one. When I click "get" it asks me to put in my iCloud password. When I do, it just won't accept it.

I've even tried installing something in the middle e.g. Sierra from the apple website as a disk image but it says the software cannot be found

Any help would be much appreciated!

Thanks