could you please clearify what you mean when you say "I want sign my air apps.how to do it??"
what do you mean sign... are u trying to create signature for a certificate during pakaging of your application?
if thats the case it depends on the type of framework you are using to compile your air application . Are you using Flex, Flash or Ajax to develop an AIR app?.
or do you want to publish your application onto the adobe air market place?
if thats the case you need to register as a publisher and add an offering.
if its none of the above then i might have misunderstood what you are requesting...
Europe, Middle East and Africa