My dryer in not heating up. How do I fix this problem?

Assuming that the dryer turns on, yes? If so, there are a number of things that could be causing the problem. Bad heating element, bad limit switch, disconnected or burned plug wire, supply wire, breaker. Most of the time it's the element or limit switch. You will need to have someone trouble shoot the system if you do not have a volt ohmmeter. Do not just start probing around, you have 240 Volts there which can be dangerous.