Because simlive is set up a like a live stream, you cannot preview it before it is live. You can, however, preview the the video itself by clicking on the file in the Media area of the platform.
One great thing to double check when previewing your file before you schedule it is the bitrates. If you are using Chrome, you can double check to make sure that the bitrates are appropriate for playback.
Click on Media, then click on the file name you would like to preview. The edit window will slide out from the right side of the screen.
If you go to the little player window, and click on the gear/settings icon, then auto, it will show you the bitrates that your file has been uploaded/transcoded with.
If you have the Premium plan, you'll see lots of bitrates, like in the screen capture above. Pro and Pro+ plan should have two bitrates. You want to make sure that the highest bitrate isn't too high or low, somewhere in the 2500-4000 range is good.
This is actually a good example of a poor upload, because you can see the bitrate is much too low. 490 kbps will not give a great quality stream. I would want to reconfigure this to a higher quality and re-upload.