Hi tizdaz,
Welcome to the forums! 
You can’t post at the moment as you just joined! Click on this thread that explains:
There’s also lot’s of useful information at this link to help get you started:
Latest Official Microsoft Flight Simulator/Forum Navigation topics - Microsoft Flight Simulator Forums
To enable Replay Mode, from the Welcome Page, choose Options | General Options | Experimental | Replay Tool: ON
{There is no need to turn Developer Mode on in the Developers Tab}
Then, once you have started a flight, you can enable Replay from the widget settings:
Hope this helps!