Texture pack installation
To install a texture pack, first open Minecraft, then, go to your downloads folder where your texture pack(s) are. Then leave them zipped format, and drag and drop them into your minecraft texture pack folder.
Okay, this is a bit more complicated. First, Download your mod from wherever you get mods from. Then locate your .minecraft folder by pressing "start" and searching %appdata%. locate your .minecraft folder and open up the bin folder and open the minecraft.jar file using Winrar or 7zip. Then open up your mod using winrar or 7zip and drag the .class files into the jar file and delete the "meta-inf" folder in the jar. then close out your windows, open minecraft and play! (note: Minecraft should NOT be open while installing mods. make a backup of your saves and bin folder in case it doesn't work.
To install a world, you first need to unzip the folder using winrar or 7zip. Then, locate your .minecraft folder by pressing start, and searching %appdata%. Then go to the .minecraft folder and find the saves folder. Drag the folder of the world into the saves folder and enjoy!