[Plugin: NextGEN Gallery] how can you scale images?

Hi I am trying to figure out how I can scale the nextgen gallery/scroll gallery so it will scale with the div box its placed in. I want to do this so i can showcase large images on large screen but be able to scale down for 800×600 displays and even phone size.

currently, it is all the same size so on large resolutions the images are too small and on phones they are way too large

https://www.ads-software.com/extend/plugins/nextgen-gallery/