Easy way:
Search outside Ogre Village and look for 2 willow branches, take the branches to the two-headed ogre inside the dark forest, they will speak on entering, place the
branches in the fire, and then take out the dragon tooth necklace from the fire, wear it.
Correct way:
Acquire both placke and hitea seeds from Thelma's Plant in the Towne of New Rigel and take them to Pelunia in Ogre Village. She will give you a pinecone for each. Plant these in the quiet glade and wait for the trees to grow. With enhanced strength, push the trees to obtain 2 branches, then follow the same steps as above.