Web Designer - Enter trigger a button on a popup

Hi,

I'm usong the web designer to customise the interface for my customer.

When I'm opening a popup I would like that when I type "Enter", then the popup closes and the action is triggered (see below)

Image may be NSFW.
Clik here to view.

I tried adding a HTML attributes to do this but without any success Image may be NSFW.
Clik here to view.

Dou you know where can I define this ?

Thanks for your help,

Regards,

Steph.