First published date error?

[Bex]

I was attempting to add a cover to my edition of this book (this one) and as I clicked save it came up with the error "publish date can't be before first published date" which I hadn't changed from the currently listed 1992 date.
I've since gotten out my book and it states in the front "This one volume edition first published in Puffin Books 1990".
Anyway how does one go about changing the first published date on a book so that this 1992 date stays correct once I upload the cover? I did have a poke but I must've missed it, thanks!

[Sandra]

At the bottom of the edit screen are the fields for the first published date.

[Bex]

I didn't even see that & now I feel a little silly. Thank you :)