How To Unblock A Publisher

Getting Message Publisher Cannot Be Trusted - Unable To Install App

Trying to install irfanview.....get error message untrustworthy publisher...

researched ed how to solve this, but having no luck, have unblocked file and running as admin...

tried ed elevated command prompt and Net user administrator /active:yes

this enables the admin login and I am able to install without issue, but select for all users.