Instructions
Open your RuneScape bank. Withdraw an unstrung symbol. If you do not have one, you can buy it from the silver merchant in East Ardougne. Unstrung symbols are occasionally available on the Grand Exchange. Another player may be willing to sell one to you. You can make an unstrung symbol yourself if your crafting skill level is at least 16.
Withdraw a ball of wool from your bank. If you do not have one, withdraw your shears and head north out of Lumbridge to Farmer Fred's sheep pen, just beyond the combat tutors facility. If you don't have shears, go into Farmer Fred's barn next to the sheep pen. Pick up the free shears that spawn there.
Go through the gate into the sheep field. Use the shears on a sheep. If it runs away, try a different one. You will receive a piece of wool in your inventory when you successfully shear a sheep.
Go to the spinning wheel on the second floor of Lumbridge Castle. Use the piece of wool on the spinning wheel. It will disappear and be replaced by a ball of wool.
Use the ball of wool on the unstrung symbol. The wool will disappear and a strung unblessed holy symbol will replace it.