You have two valves you can access here:
The round knob on the bottom controls the flow of steam/water in/out of your radiator. This should typically remain fully open unless you are servicing the radiator.
The white, numbered knob attached to the air release valve is a thermostatic valve that allows you some control over how much heat this radiator receives. When the surrounding air temperature is below its set point, the valve opens. This allows hot steam rising through the pipe to enter your radiator, which then heats your room. When it's already warm enough around the radiator, the valve is closed and steam is blocked from entering your radiator.
Now let's look at the sources of noise and how they might be addressed. Unfortunately, these are not likely to be easy fixes.
Banging pipes when the heat comes on are caused by the thermal expansion of the pipes as they are rapidly heated from inside by steam, and later contraction as they cool. The banging usually is caused by the pipes rubbing against surrounding objects such as structural wood, pipe hangers, floor penetrations, etc. Use of proper supports and bushings that allow for expansion can help reduce this, but because the pipe itself conducts sounds it is important to do this along the full run of the pipe, not just in your apartment. It's possible you could make a small difference by widening the hole in the floor that your radiator pipes rises up through, as it looks like it might be in contact with the floor at the left, but it's hard to tell for sure.
Hissing from the air vent is unfortunately somewhat unavoidable in this type of system. However, blockage of the vent hole could increase the volume of noise (by forcing the vented air/steam through a tinier hole). You can clean the vent a bit with a cloth. If the air vent valve is blocked due to accumulated calcium deposits, you may have some success in quieting it down by removing it and soaking in vinegar as described here. (Remember to shut off the supply valve before you attempt that.) Your valve looks reasonably new, so I wouldn't expect this to make a huge difference -- either way your system depends on steam venting through that little valve.
The radiator itself clicking/knocking when the heat comes on is the same expansion issue as with pipes, just manifest with your particular radiator. You may be able to help this somewhat by repositioning the radiator somewhat, or perhaps sliding some cedar shims under its feet to allow it to move a bit without creating as much noise.
Assuming it's not possible to fix all the pipe supports/penetrations or replace the system, the likely most effective thing that is under your control is to simply not use your radiator. If you are not too cold, then you can turn your thermostatic valve to its coldest setting (probably marked 1). When your radiator is closed, it will not heat up significantly, and will not vent steam. This will eliminate the hissing noise and reduce clicking/knocking from the radiator itself. It will probably not make much difference in the banging pipes because the pipes are still being used to conduct steam to other nearby radiators.
Unfortunately, these noises are pretty common in steam-heated buildings. The advantages of steam heat are that it only requires one pipe to each radiator, and it provides some humidity for your space. But it's kind of inherently noisy, and newer steam systems are not as efficient as hot water hydronic heating. That's why you mainly see steam systems in older buildings where replacing the whole system is impractical. So... have you considered earplugs?
