How to install History of Spaceflight:

0. Be sure to have the latest version of Contract Configurator installed.
1. Unzip contract packs to a new folder.
3. Copy the GameData folder into your main KSP directory.
4. When updating to a new version it's best to delete the previously installed HistoryofSpaceflight as well as ModuleManager.ConfigCache, and ModuleManager.ConfigSHA from your GameData folder to make sure it loads the new contracts that were added.

OPTIONAL 1: Soviet, US and international missions are fully separate. 
You can safely remove any of these submaps (from Gamedata\ContractPacks\HistoryofSpaceflight\Missions) if you do not wish to use them.

OPTIONAL 2: In addition to nations, certain programs within nation packs can also be safely removed - though certainly not all! 
Examples which can be safely removed are the lengthy recon programs of both the US (KH1-KH8) and Soviets (Kosmos). 
An easy way to check if a program/contract you want removed has dependencies: 
Remove the contracts, load the game and check in the contract configurator debug menu (Alt+F10) if any remaining contracts show up in red text. 
If so, you just removed a dependency. 
You can then either reinstate the removed contracts, or remove the dependency from within the contract(s) that gave the error - this can be done inside the specified contract cfg file.


SKIPPING AHEAD: Another way to avoid contracts or skip ahead to contracts you want to do is by using the CC debug menu. When in the main KSC view, press alt-F10 (by default).
Navigate to the History of Spaceflight contracts and find the contract you want to do. It will have a CompleteContract requirement with a button next to it. 
Simply press this button to disable the requirement, allowing the game to load the contract to be directly available. You may need to fastforward a bit for it to load.


Kerbalism Users: Many contracts in this pack have scientific objectives. Kerbalism changes some of the science definitions involved or the way the experiments are run.
The result is that many of these contracts either don't load at all or are impossible to complete. 
If you still want to use this pack with Kerbalism, you can manually remove the affected science objectives OR disable them through the CC debug menu. 
Remember to do so before taking the contract or it will fail.