Safari 5 Extensions Question

[Sandford.]

I was trying to install the gmail reader extension, but it told me that I don't have Extensions enabled. I know it's probably staring me right int the face, but how do you enable extensions? I've gone through pretty much everything I can think of and Safari help is no good at all.

Thanks

 

[GGJstudios]

On the Develop menu, which is enabled via Preferences > Advanced

 

[Sandford.]

Wonderful, thanks!