You do need to be shooting images.
As already eloquently stated shoot where you are.
None of us consistently have the opportunity to shoot in iconic locations.
While sketching landscapes can be useful in undestanding composition there are other factors to consider:
Cameras don't see the world the way you do - sounds silly but it does explain, to a degree, why people often struggle to capture, with their cameras, what they saw with their eyes.
So, learn to look and see in the way that your camera does - I know of no other way apart from shooting consistently.
As a general statement learn about ALL the controls on your camera to the point that you are the manual - many startlingly beautiful landscape images were shot in lighting conditions that lasted only seconds, messing around with camera controls often means missing the shot.
Understand YOUR camera's sensor - dynamic range, headroom, noise characteristics, ISO performance - learn to leverage this information to optimize file quality.
In summary it is vital to know your tools, the technically merely informs the creative, and shooting regularly with experimentation in mind is the only way to improve the creative artistic bottom line.
BTW there is nothing exhaustive in the issues that I have sought to highlight - the main message is that learning about landscape photography means shooting lots of landscapes (whether this means urban landscapes or iconic wildernesses).