It is not an option that's exposed by the IDE, you'll to turn it on by running editbin.exe in a post-build event. This answer shows the commands you need to use.
Do note however that it is fairly likely that you are wasting energy on this. It will only have an effect when the operating system can provide an execution environment that supports "large addresses". That used to be possible many years ago with the /3GB boot option but has stopped being useful a while ago. Also very detrimental on servers, they really need the kernel address space. It is still useful when your server boots a 64-bit version of Windows, any 32-bit code can get a 4 GB address space if they are linked with /LARGEADDRESSAWARE. But if you have such an operating system then changing the project's Target platform to AnyCPU is certainly the much more productive way to take advantage of the much larger address space you get in a 64-bit process. Maybe that doesn't apply in your specific case but is otherwise the best general advice.