How to Upload SWF file?

Try reviewing https://www.ads-software.com/support/topic/new-security-restrictions-on-361?replies=9#post-4647433

Thanks but I couldn’t find the word mime in my fucnions.php file

Theme: Twenty Twelve: Theme Functions (functions.php)

Any ideas where it might be hiding?

Thanks.

Do not edit the Twenty Twelve theme itself. First create a child theme for your changes.

Thanks. Should I then add that code to the new child functions.php?

Yes – that should be fine.