GIMP (GNU Image Manipulation Program) is a free program that you can use for photo retouching, image composition and image authoring among other things.
GIMP can be used on different platforms (Windows, Linux, Mac) and for a wide variety of tasks. It can be extended with additional plug-ins.
GIMP has an active user community and support material; instructions and tutorials can be found in abundance online.
This task will give you a flavour of how GIMP might be used in your research. You can try this task on your own, although it was designed to be done in a classroom with a teacher to support you.
For this task, you will need GIMP (version 2.6.10 or later) software installed on your computer. Talk to your IT support person about this.