STEP 2:
Now select the area which you want to remove. In this photo I want to remove the sky so I am going to select that. You can choose any selection tool. I am going to use quick selection tool because in my photo sky is totally blue and it will take not more than 3 seconds to select the whole sky.
Once you have selected that, invert the selection by pressing ctrl+shift+I/cmd+shift+I.
After that press F7 for the layer panel. In the layer palette click on add layer mask.