Slayer lamps are obtained from the Slayer Point Exchange Shop,
to get the lamp you will need 15 slayer points that you can get from doing slayer tasks, you can get a slayer task from the slayer duradel. The slayer tasks will vary from a differnet range of monsters according to your slayer level, the points will also vary according to how difficult your task is, you can get from 1-5 points from completing a task on top of 10,000gp per slayer point you receive. When you have the lamp, you will need to rub the lamp and then choose the skill you wish to add xp to, you
get 100,000xp per lamp.