Replace slideshow images within Network Solutions hosting package

I had my site professionally developed and had it transferred to Network Solutions, now I want to change the Slideshow images on the home page but I can’t find the images in the WordPress dashboard or in gallery. Where are they located? It’s as if the home page is locked from being modified. I did find on the Network Solutions file manager the image files, wp-content>themes>ndic>images>slideshow>slide1.jpg . I just want to exchange the images and have the replacements still show at the same speed and in the same size. In the file manager I can upload or delete files, however, deleting a file does not automatically replace it with the newly uploaded file. I called a local web designer to inquire about the change and that went nowhere, except for an hourly fee they were willing to charge me if I choose to have it fixed. I know nothing about coding. http://www.activatethemind.com