Is it possible to use https?

Unfortunately I do not quite understand what you mean by "https".

Did you maybe mean that you are looking to secure your jotforms?

If so then please see http://www.jotform.com/help/63-How-can-I-receive-SSL-Submissions.

If you meant something else then we would request that you please return to you thread here and explain more about this issue so that we can help you better.