Thanks for trying to help me. I have to have my ISO set to 200 and use manual settings for an assignment, but all my images are coming out black (or almost black). I have tried in my living room and in a train (early morning but the train is quite lit). What are the best camera settings to fix this and shoot the most versatile range of photos? Like in ordinary light? Thank you!
The camera does not see things like you do; making you understand this is probably the point of the assignment.
Your living room or the morning train are well lit for your eyes, but not for the camera at ISO 200. You must go outside when there is plenty of sunlight (that's well lit) or use a very long exposure (just opening wider probably won't be enough).
Most likely, you're setting the shutter speed far too fast for the ambient light. Use Program mode on you camera as a light meter to work out the approximate settings you should be using, then go into manual mode to tweak them as appropriate - assuming you understand the exposure triangle. If you don't, read the linked question first.