A few things new WordPress users tend to look around after installed their fresh WordPress system. To be frank, WordPress isn’t the most user friendly content management system (or blog system whatever make you happy).
There are reason why you should setup the media sizes of your WordPress. Keep in mind, WordPress will automatically crop any image you upload to 3 sizes: Thumbnail size, Medium size and Large size, another one is your default size.
After setting your WordPress and installed the shinny fresh theme, now it is time to setup the second most (literally) important setup for your website.