I am placing image that is roughly 3000x5000 px in size into a much smaller image frame roughly 300x300px. Even though the original image is much larger than 300x300 px the image looks very low quality in preview. There must be a way to have this size of an image in a 300x300 px image frame and have the quality of the image still look great. please help!
I am placing image that is roughly 3000x5000 px in size into a much smaller image frame roughly 300x300px.
Exactly this is your problem! An image of these dramatically oversized dimensions has to be sampled down by Muse during output, because (a) the browser needs the exact image size and (b) not doing so, would prolong page load time heavily.
If you best possible image quality (what means your output image is identical to your input image), please read these links thoroughly:
or this one about image optimising in Muse (post 4):