After hours

After Hours horrors Help please

Hey so I put and order on hertz on premarket. The order never went through, it caused me confusion on the rules of pre and after hour. How do I join a stock during pre market and after hours. Robinhood has been quite a head ache considering it cost me a 100$. If someone knows the rules of orders and pre markets please help me . How do people jump in companies during these hours, and why was my trade cancelled.