Creating an MP4 with audio using storyline and replay

Hi

I need to create a short MP4 video file based on a storyline presentation.

I understand that to create the MP4, I need to record the storyline output using Replay but when I do that, the sound that has been recorded onto each slide in Storyline does not come accross propertly. I also want to add background music accross the whole file.

Can anyone please help?

Thanks and regards

Susan