Killua11 has made a helpful thread with all the locations of the scattered Time Line Pages.
For this you will have to collect all 131 pages for the Ninja World Timeline. You can get these by collecting them off the ground in the Ultimate Adventure Mode. This is a side mission that is at the start of the game on your way to Ichiraku's. You will acquire this Timeline from Shikamaru's father, Shikaku. If you took one route for a Hero or Legend, you can go to the opposite direction from the Ninja World Timeline to complete the route you did not take.
To unlock the first half of Shippuden and the boyhood sections, you must do the secret actions in the battles.
Scattered throughout the free roam world map you will find Ninja Timeline scrolls. In order to get the first boyhood Scroll for your World Ninja Timeline, you must do all of Sakura's And Kakashi's side missions. After you have done this, they should appear within the training grounds. After you complete that, you will get the first battle in the ninja Timeline for the First Series section.
The side mission Residual Chakra Collection rewards 2 different Timeline pieces:
Earning 5,000 Chakra Fragments will unlock the story Eternal Mangekyou in West Land of Lightning. Completing the victory conditions for the battle will earn you the first. Should you miss it in that chance, you can replay this battle from you Ninja World Timeline. Collecting 10,000 Chakra Fragments to finish the mission will reward you with the second.
Side Missions To Do For First Timeline Scroll (Missions in order):
•Sai Battles - Client: Sai (Around the forested area right before you come to the Konoha Gates)
•Super Maiden Showdown - Client: Sakura and Company (By a store to the right side of Konoha)
•Between a Rock and a Hard Place - Client: Kakashi (By Hokage Monument)
•Memory of A Certain Day - Client: Sakura and Kakashi (In Training Fields)
To start collecting Chakra Fragments, you must talk to the frog next to the Hokage's Mansion in order to start a side mission in order for the Chakra Fragments to show up.
Free roam is available Post game So don’t worry about getting these collected as soon as you can.