There is a lesson in the Foundation course about aperture. You could check that out.
Also there is a lesson in the Explore course on background blur, which you get a lot with your aperture.
But no, changing your aperture isn’t hard at all. And if you’re just getting started you could even use aperture priority mode, which makes it even easier!
Welcome to Lenspiration, Sarah! Like Hannah said, you should be able to easily adjust the aperture on your DSLR and can learn all about that in the courses she mentioned. If you still aren’t sure how to do it, though, feel free to ask follow up questions on that!