okay guys, come on. Even if he is unfriendly let's try to help him out as good as we can:
1. The manual is available on Steam. Right click on the game in Steam and select "view player manual". If the player manual does not show up, look at the link in steam and copy it in the webbrowser. The reason for the manual not showing is steams or adobes fault, don't know. The manual is there, steam just refuses to download huge PDFs.
2. The neutrality/threat system is in place to simulate that you can't make decisions against your country. You might want to wage war against your neighbour, but, if you don't have a reason, your people, Generals, Parliament, whatever just scream "NO!!!" and you can't do it.
You want to go to war?
Two possibilities:
First: The country you want to go to war against must be a threat to you. Your people must fear the country. They must agree with your will to go to war against that country. This is simulated by threat. Your spies can increase the threat of a country (propaganda).
Second: You don't care about threat, you just want to intervene. Meaning you give up your neutrality. But this means, your country, ministers, etc must be not neutral. You have to lower your neutrality level. You can do that, again, with spies.
Now, you can declare war when your neutrality is lower than the enemies threat. So either high threat by the enemy or missing neutrality on your side allows you to declare war.
If you feel this is overly complicated, you can use the cheat mentioned above. The idea of this system is, that no unrealistic wars occur and destroy your experience of HoI3. If you want unrealistic Wars, you have to cheat.
Does this help you?
edit:
Now if you are new to HoI3, I recommend to you to play a nation that is meant to go to War, like Germany. Germany is actually very easy to play, has a well connected landmass and does not overwhelm you with a huge navy (like Italy). And after playing Germany you might appreciate the neutrality/threat system more, because it's what keeps the USA from attacking you too early or from small scale wars popping up around you.