Issue with Size of Feature Image

Hi – hope all is well. My website is having issues with speed performance and one of the main issues is the scaled images on my homepage (www.escapingexpectation.com).

i have the banner at the top of my home page, where I use a high quality image. Below, where my blog posts are listed out (bloggera template – home alternative 4) with pictures, it’s taking a lot of time to scale those larger pictures to fit in the smaller dimensions (see attached for performance review).

what i need to do: set one image (higher quality / dimensions ie. 1200×600) for the banner at the top, and another image for the blog post preview below (lower quality/dimesions ie. 288×182)

right now i only see one area for setting the blog post feature image. this is making my website REALLY REALLY slow (over 15 secs to load) and i really need a fix.

Thanks in advance, Ian.