I’d like to establish an iCloud account

To create an iCloud email account on your iPhone, iPad or iPod, follow these steps:

1. Open Settings.
2. Tap on your name at the top.
3. Tap on iCloud.
4. Toggle Mail on and press 'Create' when the pop up appears.
5. Choose the iCloud email address you want.
6. Tap on 'Next'
7. Make sure you are happy with it as you can't change it afterwards.

Did you set up an appleID when you set up the phone? It’s a good place to start