In order to swap out one weapon for another of the same type, you must use a Base Camp to access the Weapons menu. To switch weapons while playing use the D-Pad or numbers 1-2-3-4 on the keyboard. Lara can equip one of each basic weapon type at a time. By the time you reach The Acropolis level you should have acquired each of the 4 basic weapon types- BOW, HANDGUN, RIFLE, and SHOTGUN-plus the COMBAT KNIFE and the CLIMBING AXE, which can be used as a melee weapon. You gradually find and unlock more weapons as you go.
SELECTING AND CHANGING WEAPONS: Early in the game Lara has limited weaponry. Some are rewards for completing missions or reaching in-game milestones, and a few are purchased DLC. Some are acquired as you play through the game. MELEE WEAPONS This page includes a complete list of weapons, and weapon upgrades.