I want to get out of auto mode and start learning about Aperture mode. Any advice on learning with my setup? Thanks
Aperture mode is one of the best modes. Simply just set ISO and aperture to good choices so that your resulting shutter speed and flash power can do what you need done, for the specific scene.
Many users use only Auto mode, because of course they can't be bothered to learn how to do any more. Compact cameras and smart phones for example. Nothing really wrong with that, it is their camera and their choice, and it produces pictures, but if your goal is to learn photography, then Auto is the worst plan. Certainly true in the beginning, and then after the short beginning, Auto is of no use to us, counterproductive, it just gets in the way.
The first plan is to learn about exposure. Shutter speed, f/stop, and ISO.
Not meaning necessarily just to acquire a bright enough exposure, but meaning to learn how fast or slow shutter speed varies the picture, when you might specifically want either one for what it can do for you. And to learn how stopped down or wide aperture changes the depth of field of the scene, changes what we see there... to be the way you want it to look. These are the tools that we use.
This exposure stuff (shutter speed, f/stop and ISO) is easy, and it should become second nature for us. We may not always even realize we think about it, we simply just do it. Like driving and turning left at the corner, we simply just do it, long after it was necessary to think about how to do it. But it is always really good to know how. Knowledge that will be useful, and last your lifetime.
Then, even if you do do use an Auto mode sometimes, you now know how to watch what it is doing, and how to override it when necessary.
There is a lot of good stuff on line, but to grasp the ideas, a good first look is the Peterson's book
Understanding Exposure, $17 at Amazon, or our public libraries here have it. Try your libraries, they will have something.