Rotate before submission

Sometimes cameras will display pictures in its estimate of the user's intended orientation.  Sometimes the viewing software will also display pictures correctly.  However, unless you save the orientation change, the file will remain in its original orientation.  When you transfer the file, it will be in its original orientation.  I have had this happen when I have taken pictures at odd angles, as in from under a small plant or other object.

As Mat has already said, you can change the orientation and save the picture in the new orientation using any editing software.  Nearly all cameras are sold with editing software.  If you use your phone, you can download an editor OR you can transfer the picture to your computer and edit it there.  Remember the preferences of your customers here.  Beyond the reorientation, refrain from any other editing.

The best software other than Photoshop that I have used is the free software GIMP which stands for "GNU Image Manipulation Program".  It is available on Sourceforge.  If you have not used this website, just pay attention to what you select.  You will not get malware, but you could end up on a trip around sponsored links.  It is a free website that does not require membership to search and download software, but it is supported by ads.  The same is true of some of the publishers.  The fully functional software is provided with no strings attached, but since far fewer people contribute than should, they also have sponsor links.  This enables them to continue to write and originate outstanding code at no cost to users.

I hope this helps.