How do I download a Texture pack in Minecraft?

I want to download Creative One's Medieval Texture pack but I can't get it to work! I just bought Minecraft today, but my brother had a rental from a friend and already downloaded his texture pack, but the rental game was gliched. now that i have my own I can't get it to work.
Update: 2 more things.
1. I am on a PC
2. Where should I download it from?
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