# He himself

This refers to Jesus, with emphasis. 

# carried our sins in his body on the tree

Here "carried our sins" means he suffered the punishment for our sins. Alternate translation: "suffered the punishment for our sins in his body on the tree"

# the tree

This is a reference to the cross on which Jesus died, which was made of wood.

# By his bruises you have been healed

"God has healed you because people bruised him"