You can add new staff testimonial through Testimonials → Add New Testimonials in the WordPress Administration Panel.
Testimonials contain most of the same options as standard posts. You can read about these in the Add New Post chapter. Additionally, they contain post options specific to testimonials.
Testimonial Options are found below the editor on the Edit Testimonial page. If the Testimonial Options are not visible, make sure they are checked inside the Screen Options area at the top.