How to have two macs on separate iCloud account

Do you want to have separate iCloud accounts on separate Macs, or why are you asking?

When you set up your user account on a Mac you select the AppleID you want to use in the user account. You should use the same AppleID for the same purpose - for example one AppleID for all private purposes in all your private user accounts on all Macs, maybe a different Apple ID for work in all your user accounts related to work on all Macs. You can share purchases between up to five AppleIDs with family sharing.

In your question - how to have two Macs on separate iCloud account , if they are signed in with same Apple ID and password on the same network , sign out the desired Apple ID https://support.apple.com/en-in/HT208242 from Mac system preferences

And sign in with a different Apple ID in the empty field https://discussions.apple.com/docs/DOC-13561

Read this also https://support.apple.com/en-in/guide/mac-help/mh36825/10.14/mac/10.14

The second Mac will be still signed in with primary Apple ID address .

Another way is you can remove the second Mac see the article https://support.apple.com/en-in/HT205064

In the article they are describing about iPhone , it can be applied from Mac also .

The method to sign out and sign in will differ for two factor authentication and secondary authentication account and for different version of Mac .

You can have separate iCloud accounts on 2 separate macs if you want to, But I would recommend only using one if you are the user of both macs.