Preview can do quit a bit more than just display images. It can also double as a basic photo editor.
Be aware that edits made in Preview are destructive, so you may want to retain the original photo for future use.
After duplicating the image you'd like to edit, open the image and click on the Markup icon. This will open the Markup toolbar.
Below are a few of the options found in the Markup toolbar:
For more information, including a description and use-case of each tool, please see: https://support.apple.com/guide/preview/annotate-an-image-prvw1501/11.0/mac/10.15