Instructions
Travel to Lumbridge and enter Bob's Axe Store. Purchase a knife from the store.
Travel to the Grand Exchange and purchase Adamant Ore and Adamant Coal.
Walk up to a tree and select the "Chop down tree" option. This will cut down the tree and add the logs to your inventory. One log with give you 15 arrow shafts. Use the knife on the logs to change them to arrow shafts.
Walk through towns or wilderness until you locate some chickens. Kill a chicken and receive a feather as an item. Repeat this numerous times to collect as many feathers as you can.
Click on the feathers in your inventory and select "Use with." Select the arrow shafts as the items you wish to combine the feathers with.
Travel back to Lumbridge and locate the furnace near the Blacksmiths. Click on the furnace and combine the Adamant ore with the coal. This will make the Adamant arrow heads. Combine the arrow heads with the arrow shafts to create the Adamant arrows.