On this page of the guide to Baldurs Gate 3 you will find an answer to the question how to light the torches. Torches are very useful when lighting the darkness, especially when your characters aren't able to see through the darkness or they don't have any skills that enable them to illuminate darkness.
Torches can be found in the game world along with another loot. They may lie in plain sight or be stored, for example, in chests. By default, each torch you collect is not lighted. Until you change that, it won't lighten up the darkness.
When you enter a dark area for the first time, the game will present you with a tutorial window. There, you will find an advice about lighting the area. Although it isn't mandatory, traveling with an active light source will make it easier for you to find interactive objects and it will reduce the risk of encountering potential threats. Additionally, it will make it easier for your characters to detect traps.
What's important is that you need a source of fire to light a torch. If you don't see any sources of fire in the area, look around for, for example, a candelabrum like the one in the above picture. Interacting with it will set it on fire.
The next step is to place the torch in the hand of one of your party members. You can:
- Find the torch in the inventory and select the option to use it.
- Open the character's equipment menu and switch the currently used weapon in character's hand to a torch.
That's not all. You must select the Dip action from the bottom bar. Then, click on the fire source, for example, the previously mentioned candelabra.
If you have completed all steps correctly, the torch should be set on fire.