When you insert an image, you can choose from some preset sizes. Thumbnails are 150×150 pixels, and, depending on the original size of your photo, go up from there. Depending on the size of your original image, WordPress will choose to crop the photo to prevent the aspect ratio from getting warped (to prevent an image from looking stretched, which you may have seen on other photos). If you want to prevent the cropping from happening, use the “Full Size” option when you post it to your site and that will post the image as it should be.

After you insert the image, you can then scale it down if it is too large. Click on the image. In the top left corner of the image you will see 2 icons appear – one for edit the image and the other for delete the image. Click on edit the image. In the popup, you will see the image and a number of options, including the option to slide the size of the image from 100% (the original size) down to 60% size. Using this, you can reduce the size of the image without affecting the aspect ratio.