In order to add a progress bar in the kanban columns, you will need to add a progress bar tag in the kanban view definition, as follows:

<progressbar 
    field="popularity"
    colors='{"low": "success", "medium": "warning", "high": "danger"}'/>

Note that kanban column progress bars were introduced in Odoo version 11. Versions prior to that will not display column progress bars.

Restart the server and update the module to apply the changes. Then, click on the plus icon in the column. This will display the progress bar on the kanban columns, as shown in the following image: