Why is my cpu overheating?

Is fan working?
Try factoring resetting bios settings.

Did you use thermal paste? And add enough?

Make sure the cooler is mounted properly to the motherboard. It doesn't have to be extremely tight

Is the processor one with an embedded GPU in it? Are you playing off of this GPU, or through a discrete GPU? If you're playing through the embedded GPU, then it's likely the embedded GPU is responsible for the temperature.

Also, it's important to close the case up. The closed case creates a venturi effect which increases the flow of the air through the case, thus increasing heat transfer.