How to enable free tagging?
I do not know what a free tagging cloud is, but I can help you with setting up a free tagging field.

On your entity (content type), add an entity reference field that references taxonomy terms. Optionally you can limit to a specific vocabulary. Also select the checkbox to create new items if they do not yet exist.

Then on the manage form display tab of the content type, make sure that you select the Autocomplete (Tags style) as the Widget for your created field. This should give you a free tagging text field.

(You can use the Article content type of a clean Drupal site as example)