Firemaking is a skill which you can set objects such as logs or lanterns on fire.Fires can be used for cooking things such as meat and fish on the spot.
In order to make a fire,you need a tinderbox and logs.You can use a bow,a forge regent,or a dwarven army axe which is a multipurpose tool as well.you can gain logs by cutting trees,or buy from the grand exchange.All bows can be used except ogre bow,ogre comp bow,dark bow,and crystal bow after barbarian training.You can buy a tinderbox in the general store in Varrock, Falador or Lumbridge.
Players often train firemaking skill at Fist of Guthix by using the tinderbox with the logs in your inventory.Your character will bend down and attempt to make the fire.Once you move away,your fire will be lit.With your firemaking level up,you can burn higher level logs.