The Avatar is huge compared to a human as well as being blue & having a tail. They a physically much larger & stronger than we are. In order to take control of an Avatar one must link consciousness with it by lying down in a machine designed to allow you link you. Once inside of the new Avatar he finds he had the use of his legs which is wonderful for a man who has not been able to use them for so long. He really enjoys the new body & soon finds himself on his first mission outside the base. He is separated from the group by a wild beast that he stumbles across while acclimating to the new environment.
He must spend the night away from the security of the base & soon finds himself in a lot of trouble. After dark he lights a torch to be able to see in the dark but that attracts the attention of a pack of wolf like creatures who are now interested in ripping him apart. He is militarily trained but a whole pack is hard to defend by your self & soon finds himself in a world of hurt. Luckily for him he has also caught the eye of another, a female of the indigenous species he was told about earlier. She was going to kill him but her God gave her a sign that it should not happen so instead she jumps into action to save him from the pack.
After she saved him she tells him having the fire is attracting the unwanted threats & she puts it out. Suddenly the night comes alive with illumination from the plants surrounding them allowing them to see fine. She takes her to her tribe because of the sign & has to introduce him to her family & friends who are not immediately accepting but since they have never seen a warrior in an Avatar body they decide to communicate with him & show him their ways. He comes to love the traditional ways of the people & he longs to help them but all the while he is reporting back to him commanding officers.
The world is turned upside down by the chaos that ensues. The two species go to war & with the help of not only Jake Sully but some other humans who joined the opposing side of the fight they are able to turn the tables on the humans. When the planet joins the battle to help defend itself there is not a lot more that can be done. Not to ruin it for you altogether but some of them were not completely satisfied with the way everything turned out!