All Testimonials option is available in admin panel >> Testimonials >> All Testimonials. 
If you will add your own Testimonials(s) in your theme , then Testimonials list will be show here.
From on hover on any Testimonials you will get below given option(s)
1. Edit :If you will hover on any Testimonials in list, you will get edit option edit, by clicking on that you will be on edit Testimonials, from there you can edit Testimonials info like featured image, Testimonials Link, Testimonials title / name, Description, Social URL(s) etc...
2. Quick Edit : By Quick edit you can edit some most information(s) like Testimonials Title , Slug , Status etc...
3. View : View Option is for view your Testimonials. If you want to see Testimonials with your matter like Title , Description etc... you can use this option.
4. Trash : Trash option is use for delete Testimonials(s).
Bulk Actions : [2,5] You have all Testimonials(s) list in below given image , if you want to take bulk action on one or more then one Testimonials(s) , you can mark[3.1] and select Your bulk action like delete[2,5] etc...
** If you want to add a new Testimonials you can click on Add Testimonials option.