If you have a look at the portraits of your NPCs, you will see a little arrow on the right frame (and possibly on the left frame as well, but I'm not certain of that - it's been a long time). Click on the arrow on the right frame, and the portraits will scroll over. Continue doing that until you see the golem portrait, and then click on that. IIRC, the golem parts should assemble themselves (actually, your golem NPC does it), and when you get back to your castle in Harmondale, you will see your golem patrolling the main hall, protecting your party's property. If you've done it properly, the golem will attack any monsters hostile to you which get into the castle.I should add that if you've used the wrong head, the golem will attack your party ... 
