2D Animation Help

Hello Blender community. I recently moved from Opentoonz and now using blenders 2D animation interface to do my work. Having a bit of issues and I scoured the internet for the basic tutorials. Some of them helped alot but the one thing I can get is how do you select key frames? Does the yellow cursor on your timeline indicate a key frame? If so, how do you create more key frames, extremes, and inbetweens?