Switch over to the Design Section to start editing your images. Click on it to expand the different options:
Caption: Add a caption that will automatically be placed under your image. If you don't add anything, it won't be displayed.
Crop: You'll find here several options to crop your images in different shapes or to don't crop it and keep the original dimensions.
Size: This sizing bar will control the size of your image.
Text size: Use this bar to change the size of your caption.