Angry Omnath is like Regular Omnath, except ANGRY!
Playing Omnath, Locus of Rage is like playing an playing an avalanche, if an avalanche was a magic deck! The main idea of the deck is to put as many lands onto the battlefield as possible to trigger Omnath, Locus of Rage's Landfall ability. His ability lets you create a 5/5 elemental token whenever a land enters the battlefield. In addition to smashing your opponents with a horde of big creatures, you also play spells like Purphoros, God of the Forge, Warstorm Surge, Where Ancients Tread, and Impact Tremors. These cards let you deal damage to all of your opponents whenever a creature enters the battlefield under your control, which will happen a lot.
To get to the point where you overrun your opponents with 5/5 elemental tokens, you need to have a lot of lands enter the battlefield to trigger Omnath's Landfall ability. To do this, you play spells that let you search your library and put lands onto the battlefield such as: Cultivate, Kodama's Reach, Sakura-Tribe Elder, Harrow, Splendid Reclamation, Explosive Vegetation, Nissa's Pilgrimage and Scapeshift. These spells will let you get lands from the library to the battlefield fast. In addition to these spells, creatures and enchantments such as: Exploration, Oracle of Mul Daya, Azusa, Lost But Seeking, Mina and Denn, Wildborn, Burgeoning, Ramunap Excavator, Khalni Heart Expedition, and Into the Wilds will let you either let you play extra lands per turn or put extra lands onto the battlefield for you.
Now that you have all of these fancy lands and 5/5 elemental tokens, where do you go from there? Well you obviously want to attack your opponents with them, but how can help them do that? Enchantments or creatures such as: Fires of Yavimaya, Anger (in the graveyard), and Hammer of Purphoros will give your elemental tokens haste so that can put out as much damage as possible as quick as possible. One way to put on a lot of hurt quickly is if you happen to have a haste enabler out, play Scapeshift, put a whole bunch of lands from your library out onto the battlefield, then play Splendid Reclamation to get all of the lands you sacrificed to Scapeshift back onto the battlefield to create a stupid amount of tokens. Bonus points if you have Doubling Seasons and/or Parallel Lives out and/or play Second Harvest to get more tokens than you can count!
I hope this description helps anyone who was confused on how the deck works. I feel once you play it a couple of times, it will become pretty straightforward to play.