How can I set up my iCloud account?

To set up iCloud in Mac , you need a web mail address that can be created using some services like gmail https://support.google.com/mail/answer/56256?hl=en

It has to be signed in Mac system preferences , make sure Apple ID address and its password should be kept same as web mail address and password .

Turn on inbuilt applications to sync .

See some articles Set up iCloud on your Mac - Apple Support

Set up iCloud features on Mac - Apple Support

Set up your Apple ID iCloud settings on Mac - Apple Support

You may want to reply with more information about what you are trying to do. iCloud includes a variety of services and there is no single setup option.