I can’t start using my ICloud what do I need to do?

Have you signed into your Apple ID in Settings/Your Name/iCloud and turned the desired syncing on? if you can't do that, what happens when you try? Error message(s)?

Some other things you can try. Do you have access to another WiFi network where you can try? That has worked for several people.

Try a restart.

Restart your iPhone, iPad, or iPod touch         

Try a forced restart.

Reset Device.      

If necessary

Hard reset.        

Do a backup and try a factory reset. Then restore from your backup.

Restore to Factory setting.      

Backup - Restore your device from an iCloud or iTunes backup.