How to install minecraft texture packs?

Okay so I tried installing some for my sister yesterday and it was so stubborn and could not do it. What ways can I install it? I have windows 8.1 and I wanted the texture packs from Planet Minecraft. Hope you can help, thanks!

Added (1). Okay, thanks! Yesterday I spent probably 2-3 hours and I had it in the minecraft folder but it would not open up. It said it was "zipped". My dad is a computer geek, and he couldn't even find it out! It was so frustrating but I'll definitely try again after my schoolwork. Thanks!

Added (2). @ Sean, that's literally what I did yesterday about a 1,000 times but it would not open the file and it wouldn't appear next to the default like it should.

First you get the texture pack then on your start menu type %appdata% then go into roaming. Your.minecraft folder should be there. Open the folder and then open recourse packs then put the texture pack in there

Ok so all you have to do is search for run, and type %appdata% and look for your.minecraft folder it should be up at the top of the list, then open that folder and look for resource packs for the new version or texture packs for the older versions then drop the.rar file in there and start up minecraft and select the texture pack. Hope it helped.

Download the texture pack your sister wants then all you have to do is if you have the latest version of minecraft. Go to video setting in options when you load up minecraft and you will see a button called "Resource Packs" if you open it the only thing that will be in there's one called "Default". Press the "Open Resource Packs Folder" find where you saved the texture pack you want to install and just drag and drop the texture pack file (which should be a.zip file) into the "Resource Packs" folder you just opened. Once you have dragged it in go back to minecraft and you should now see the texture pack under the "Default" one. Just click the one you want and minecraft should load the texture pack and you should be ready to play with your installed texture pack.