Image sizes on theme ePix

Hi all, I purchased the ePix theme recently and I am having a difficult time resizing the images. Images are not fitting properly on the “slide set manager”. I have tried resizing them smaller but they are still showing up extremely huge on the page and between the display of the pictures, the pictures are jumping. Currently, I only have five pictures on the slider since the sizing is giving me trouble. The site is https://www.piixdot.com.

Also, in the beginning of the installation of the theme, they recommended two plugins. Only one was installed successfully, which is Advanced Exerpt. I do not remember the name of the other one.

Please help. Thanks in advance.

https://www.piixdot.com