A trial version of Photoshop is fully functional, there isn't anything that is restricted. What screen are you looking for? What functions are you trying to execute? Generally, the functions in Photoshop are executed from the Menu bar, the tools panel, or the other panels (Layers, Actions, History, etc). There is no screen for running functions. Unless you are refering to the Photoshop UI itself.
But you mention that you are able to run tutorials. What tutorials would those be? Photoshop doesn't come with any. Perhaps you have something other than Photoshop installed?
Thank you very much. I figured it out. I signed on to Adobe Creative
Cloud. I downloaded the Photshop application and saw the tutorial for
Photoshop CC there and thought that's where I should execute Photoshop. But
later I found the Photoshop icon as an App on my Windows 8 Start screen and
executed it from there. Wish I had Windows 7