These are the same steps as you would take to import contacts from any system that you might have them in, such as from Outlook, Gmail, etc.. However, iCloud only has an option to export the contacts as a single vCard, which is not very handy, and certainly not as handy as having those contacts in a spreadsheet (to potentially clean-up before import).
This video (created by someone else) shows the steps to export your iCloud Contacts and get them into a spreadsheet format for ease of working with:
https://youtu.be/gHnK9EMntos