The easiest way to understand the relation of aperture and shutter speed is to think of your sensor like your eye ball. They both work similarly and both are sensitive to light.
Your aperture is like your iris and pupil. When the light is low, think about how your iris/pupil opens up really wide to allow light to get to the optical nerve. Same as with your lens - you open up the lens really wide to get light to the sensor. When the light is bright, the exact opposite happens, the iris and pupil close down in order to protect the optical nerve.
Aperture also works with your depth of focus (DOF). When you squint and close down the amount of light hitting your iris/pupil you get everything in focus. When you open up really wide, and focus on one particular subject, everything else blurs (bokeh). So aperture effects your DOF.
Shutter speed can be thought sort of like your eyelid. When it is bright, your eyelids open and close quickly, or you squint, in order to only take in a little bit of light at a time. When it's darker, your eyelids are nice and open to get as much light in as possible.
A fast shutter will freeze action. Think of how a strobe light on a dance floor at a party might freeze action the section it fires. When you leave your shutter open for a longer period of time, the light is available to blur through - such as with movement, water, fireworks, etc. Through use of the shutter speed, you artistically choose how you want movement to be portrayed.
So based on what you know of how these things work together, you can then begin to make artist decisions on your image. Do you want a shallow DOF (open up your aperture) in order to freeze action with your shutter? Or do you want every aspect of your photograph in focus, but are willing to slow down your shutter by making some sort of concession (such as using a tripod or using your ISO which might produce noise)? Do you want to use your shutter to freeze action (fast shutter) or show some sort of motion (slow shutter)?
What you decide to use is dependent on what you are doing at the time, what you want your final product to look like and the limitations of your equipment.
For example....
Here, I wanted to isolate my subject using my DOF of my aperture:
ISO 200, f1.4, 1/2500 (notice the really fast shutter!)
Here, I wanted to make sure that everything was in focus, I wanted to use a low ISO to decrease noise, and I wanted to shoot a busy location with a lot of people walking around. So I choose a long shutter knowing that there wasn't enough light shining on the people to have them show in the photo and the long exposure allowed me to keep my ISO low and my aperture high.
ISO 200, f22, 13 seconds
Practicality wise, I wanted to shoot my toddler (who is a fast moving subject) so I focused on keeping my shutter speed higher. This froze her action her and the water movement in the fountain!
ISO 200, f2.8, 1/100
Here, artistically, I decided I wanted to show the movement of the fireworks - so I chose a longer shutter, that would give me movement in the streaks.
ISO 200, f22, 1/1.6
So for the assignment... start shooting things such as sports and fountains. When you start experimenting with these two fast moving subjects, you start to understand how your shutter works and how you can start to make artistic decisions based on what look you want to achieve on the other side.
Hope this helps!!
ETA: I just realized that I spent all the time writing this post and I didn't read yours close enough... you understand shutter. Hopefully my reply might help someone else... so sorry to write all this!!
But yeah, shoot fast moving objects, like on shutter priority, and start experimenting with long/short shutters and look at your outcome!
