Just want to know how to get a ghost amulet. I just can't work it out. It says I don't have that amulet but nowhere does it say how to get one

From AEGram's MC Game Guide:

Fall event of 2018 brought with it 3 new amulets that players could purchase:
1. Morphing Quick Cooldown – (Cost: 15,000 coins) – Cuts morphing object cooldown time in half for 60 minutes – 80 Energy Units to activate
2. Morphing No Cooldown – (Cost: 100,000 coins) – Stops morphing object cooldown time for 2 minutes – 150 Energy Units to activate
3. Ghost No Cooldown – (Cost: 20,000 coins) – Stops ghost cooldown time for 60 minutes – 120 Energy Units to activate

NOTE: The “for purchase” amulets were made available during the Fall and Winter 2018 events and during the Spring 2019 event. They have not been offered since those times.

That explains it. Maybe they will be offered again at some point.

Thank yu

You're welcome, happy to help!!