Some themes will have specific image size requirements for logos and/or product images. If that’s the case, these requirements will be noted above the image uploader, as seen below:
For instance, if your image is too tall, double-click the image file so that it opens in Preview.
Then click, “Tools” and select, “Adjust Size” from the dropdown.
Go to height, and change the size to the required height. To ensure the new size scales proportionately be sure, “Scale Proportionally” is checked. Then save the new image size.
Once your image has been resized, upload the image like you normally would in your WebStore.