Shadow of the Tomb Raider features a fast travel system, but you can't use it everywhere. Here, you can learn how to unlock fast travel in Shadow of the Tomb Raider and how the system works.
You cannot use fast travel from anywhere, First, you have to reach one of the camps.
Sit at the bonfire and a menu will open. Choose the last option - Fast Travel. Note: fast travel isn't available from the very beginning of the game, and might be unavailable during some missions. The first time you'll be able to use the system is after defeating the two jaguars in the jungle.
If the fast travel appears to be unavailable, you might have to solve the current stage of your main quest. After completing it, the option should be back.
After selecting the fast travel in the camp, you have to choose the destination. Lara can only move to those camps that have already been discovered. Always keep your eyes peeled for new caps - apart from unlocking new fast-travel points, you will also get some XP.