I Believe you need to go to your room, into your storage box and under "SELL ITEMS" I know it's weird why not under manage items. Anyway once you under "SELL ITEMS" there are 3 tabs on top so go to far right under materials.
I'm also having the sharpness bug that other people already mentioned. Aside from that the Trainer works like a charm. I still got oneshot though, despite having unlimited health active. Looks like the trainer just regenerates your health quickly rather than locking it at 100%.
Easy crafting and oneshot kill would be some nice additions to the trainer.