First, think long and hard if the person really should be deleted. If someone quits or change thier job, the best practice is to set them as inactive. If you added someone by mistake, deletion is a good idea.
To delete a person, click the context menu (top right) on the person card and then press remove. Deleting persons is a permission and if the person comes from the Bisnodes source data you can't delete it.
If you deleted a person by mistake, don't worry