With inCMS you‘ll never have to worry about resolutions and pixels again. The size and quality of the images that you insert on the website are automatically optimized. In case you don't want inCMS to optimize the size of your image, please proceed as follows:
There is a setting in the image edit window labeled "Quality". Ensure the checkbox for "Insert image unchanged" is checked.
If you want to crop your image, you can do this in the image edit window as well.
If you want to resize or crop your image outside of inCMS, check out http://www.picresize.com/. Picresize.com is a free utility that is very straight forward and can scale an image by percentage. The smaller you make the image, the smaller the file size.
All other image editing should be done before uploading to inCMS, including orientation.
Any Image editor that allows you to rotate, scale, change resolution as well as crop will serve. Having some filters for Brightness and Contrast as well as color balance is a plus.
Pixlr is another free online tool. It's great for image editing and offers many more options than Picresize.com: https://pixlr.com/