Your first mission is a tutorial which begins in a temple (1). Approach the pedestal and interact with it. Go to the next room and collect clothes from a chest. Once you activate another pedestal, a gate will open and you will be able to walk outside. Head to where an old man is located (2). Talk to him and go to the tower (3).
Look around - not far from the old man there is an axe that you can use as a weapon or to cut down trees and collect wood. You will come across some Bokoblins. Fighting them is extremely easy and once you defeat all of them, you will obtain a bow and a sword. Reach your destination and activate another pedestal.
This way, you will activate Great Plateau Tower and unlock the map of the surrounding region. Exit the tower to begin another quest. In order to get down safely, jump down using the rocky shelves.