This texture pack is 64×64 you will need to use OPTIFINE with MAGIC LAUNCHER or MCPatcher.
These programs allow you to experience all of the fun items such as :
Connected textures (turn them to ON) Bookshelves, crafting tables etc
Randomized Mobs (Really Important!!!)
Connected Better Glass (This pack has better glass)
How to Install DR Realistic Texture Pack for Minecraft
In order to use HD texture packs properly (32× and higher) you will need to either patch your Minecraft using MCPatcher or using OptiFine. Optifine is preferred as it includes all of the features of MCPatcher, and greatly increases game speeds and graphics settings. MCPatcher tends to be updated on the same day as Minecraft updates, so use it instead if you are in a hurry.