This page of our guide to Horizon Forbidden West lists all the War Totems available in the game. There are 3 collectibles of this type in total.
Totem of War
The first totem is in the western part of the map, in the snowy mountains. We recommend using a Sunwing to get there, but you can do so on foot as well.
The totem is hidden under the roof of a wooden hut. We've marked it on the screenshot above to make sure you don't miss it.
You should know that the totems are colored white when highlighted with the Focus. They're also not marked on the map, even though you must collect them to fully complete the game.
Totem of Youth
This totem is located on an island that's only accessible after completing the Faro's Tomb main quest. You can't get there by just swimming. You must use the boat you receive during the quest.
The collectible is on the destroyed metal bridge. Simply get onto it and look at the railing. The totem's there and can be grabbed without any issues.
Totem of Brotherhood
This totem is on a small island in the southern part of Cinnabar Sands.
You can easily spot it by running along the shore. It's hidden in a small hole, under a rock covered with plants. You may encounter enemies nearby, who'll try to discourage you from exploring the island.