Go to your source folder then go to src\com\rs\net\decoders\handlers
Then click InventoryOptionsHandler now put this code anywhere

    if (itemId == 23740) {// huge prayer lamp

			player.getSkills().addXp(5, 14000000);

			player.getInventory().deleteItem(23740, 1);

			return;

		}

for what ever id you want replace 23740 with your item id and where it says player.getSkills().addXp(5, 14000000); the 5 is the level id and 14000000 is the amount of xp that will be gained after clicking the xp lamp. here are the skill id's

    ATTACK = 0

DEFENCE = 1

STRENGTH = 2

HITPOINTS = 3

RANGE = 4

PRAYER = 5

MAGIC = 6

COOKING = 7

WOODCUTTING = 8

FLETCHING = 9

FISHING = 10

FIREMAKING = 11

CRAFTING = 12

SMITHING = 13

MINING = 14

HERBLORE = 15

AGILITY = 16

THIEVING = 17

SLAYER = 18

FARMING = 19

RUNECRAFTING = 20

HUNTER = 21

CONSTRUCTION = 22

SUMMONING = 23

DUNGEONEERING = 24

once your done just save compile and there you go