2-player risk is of course for 2 people with the neutrals playing, in order to play you must know the rules for domination risk which are right here and also you should know the rules for attacking right here.
2-player risk (T1)
2-player risk is almost the same as the original game with a few different additions in it. For starters there are neutral army's in which you make alliance with them depending on the game you pick. There is a passive, and an active play, passive is where the enemy does not move or attack but it can defend, it really just a roadblock. Active is far more complicated with alliance and other related actions.
For setting up the game, both players start with 36 units each, and the 4 neutrals start with 24 units each. After that take out the 2 wild risk cards and deal 9 to each player (remember the neutrals aren't players) and deal 6 to each neutral. Place 1 unit depending on what countries are displayed on your risk cards, do it for the neutrals as well. Once the units are placed, return all cards to the deck and shuffle. Roll the dice to see who places units first (roll for the neutrals as well.) Depending on the roll that player places units first, a player places 3 units a turn, and a neutral places 1 unit a turn. Players (not neutrals) roll to see who goes first.
Passive neutral game (T2)
In a passive neutral game, the neutrals don't gain reinforcements, attack, or move, they are just simple roadblocks. The game works like a normal one.
Active neutral game (T3)
In an active neutral game, the neutrals act more than they would in a passive game, for example they can be allies with a player. The positions of neutrals are allied with player 1, allied with player 2, and uninvolved. For starters your going to have to place a cannon for each neutral beside the game bored between player 1 and 2, line them up in a straight line. As the neutral position changes move it in the appropriate places, towards you, away from you etc. The turn order is still the same except a couple different additions.
The first step is to bribe Neutrals, in order to make it more favorable towards you, give that neutral a risk card, once you do move the cannon towards you, its is now officially allied to you however, the other player can do the same and make it favorable to him/her. You may give up to 2 risk cards, and you can give cards to other neutrals as well, however once a neutral has 5 cards, it can no longer be bribed.
The second step is to receive reinforcements, it's the same thing as global domination risk, you don't count the territories your ally owns as yours.
The third step is for your allies to receive reinforcements; you do not have to reinforce allies if you choose not to. If you choose to reinforce an ally, than roll 1 die, whatever you get are how many your allies, repeat it for all your allies. Allies get no bonuses for countries/continents.
Step four is attacking. It works the same way; you can use your allies to attack the other player and neutrals. Whenever you successfully take a country roll a dice, 1-4 makes the counter for the neutral you use to move towards your opponent 1 step, 5-6 does nothing. If you use the ally, to attack another ally, roll for both, but 1 at a time. If you eliminate a neutral you get all its risk cards, if you use an ally to do your dirty work and eliminate a neutral, you get the cards not the ally.
Step five is fortifying, it's the same as global domination risk.
Step six is fortifying your ally, you get one free move, to each of your allies, fortify them with the same rules as Global domination risk.
The last step, getting your risk card, you get one for conquering a territory like global domination risk, except your allies don't get any for taking countries, and you don't get one if your allies take a country, you only get one if you take a country.