The Hidden Forest

Im doing the Alt P and I learnt i could make weapons with the Cold Iron Ore and the catalyst I got in the Warrens, but when I go to the forge to combine them it says "You cannot combine these items in this container type".

Just wondering what i need to do to get them to combine, thanks

make sure you first find proper recipe in the recipe search option of the forge, and don't try to do a manual combine - you could be missing something or using wrong quantity