You have native stages and can create custom ones.
You can manage your stages in your Stages page where you can update it, delete it and also see in one click all contacts with a specific stage (1).
You can also create your own custom stages owing to the dedicated button (2)
You can assign stages to your contacts directly from the Contacts page. You just need to select some contacts then click on the Stage button (1) and select a stage of your choice (2). Click on Submit (3) to confirm your choice.
You can also assign a stage to a specific contact by clicking on the dedicated cell (1).
You can modify the same way your contacts stages directly from this page, or on the dedicated page of a contact by clicking on its current stage (2) and selecting the new one.