Can't download an application from the net because of an apple security block

Question

MacBook Pro C0*******3UG 1TB Os 10.9.5
I can't install an application from the net because of some Apple security block. How do I remove or get around the block? The instructions in help say to double click  the application and all that happenes is that I get the same window saying I can't install.
<Edited By Host>

Answer 1

It's usually not necessary to change any security settings, and as a rule you shouldn't.
To make a one-time exception to the security policy, follow these instructions. They apply to Installer packages and other installable items as well as applications.
Some defective software installers may fail when Gatekeeper is enabled. Think carefully about whether you really want to run such an installer. If you do, temporarily change the setting to
          Allow applications downloaded from: Anywhere
When the installation is done, revert the setting.
Some applications that don't have a developer signature have been reported not to launch the first time unless Gatekeeper is disabled. The warning message from Gatekeeper is that the application "is damaged and can’t be opened." Again, think carefully about whether you want to trust the application. If you do, disable Gatekeeper as above, launch the application, and then re-enable Gatekeeper. If you still get the warning, delete the application.