Step 1: Download MCEdit in the link http://www.mcedit.net/
Step 2: Run Minecraft and make a super flat world and call it something like "Schematic Tests" or something.
Step 3: Open MCEdit and you should see your saves folder and open your world Schematics Tests
Step 4: Click the Import to the left of the steve head where your hot bar would be in minecraft (Click don't scroll)
Step 5: After clicking Import find and locate where your schematic is and double click it
Step 6: Click where you want to place your building or whatever you downloaded and press the enter key
Step 7: Press Control+S to save it get on normal Minecraft Get on Schematics Test and look at your downloaded creation 

Now you can go put it on a non superflat world to maybe play a survival house on or just want a statue or something like that right next to your house in an already made world.
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Also if you have any questions or something PM me I'm an active user and I'll answer ASAP