I'm using Paintshop Pro and I have a paint kit for the C172. My problem is, when I add lettering to the left side of the fuselage rear template{ this paint kit only shows the left side} the letters are reversed on the right side. Is there a solution someone would be willing to share with a beginner please? Thank you for your time.

Assuming its the default C182, you unfortunately can't do anything with it. If you put the text on that one side and it appears on both in flight sim then the textures are being shared. This means regardless of what you do with the text it'll always be reversed on one side.