Hi,
Is there a way to make this work?
I have copied this from https://www.youtube.com/watch?v=FVARVy3YS74
I can write in the name and comment box when I am previewing - but when I click submit nothing happens.
Please help! Thanks so much in advance 
Without looking at the Wix Tutorial on that Youtube page, I can only suggest currently that to make sure that you have followed it exactly and made the right choices for the dataset permissions like form submission and not site content for example.
Plus, I would also look at calling everything the same as it is done in that video so you simply have to just copy the code used and in theory it should all work without you having to change anything to suit your own page etc and that the dataset itself is set to write only whilst the displayed comments is set to read only.
Finally, double check that all the code has been typed up correctly, easy to miss out a (, ), { or } somewhere in the code, we’ve all done that. Plus, the final thing to check if something has a submit button, is that if that actual submit button has been setup to submit through the dataset submit settings to the comments dataset itself.