Ian has no difficulty in __________ into use the perfect plans his friends have prepared for him.
Knowledge of fixed phrases
Phrase: Put (sth) into use: to put something into effect by putting it to use or functioning.
Ian had no difficulty executing the perfect plans his friends had prepared for him.
Structure to note:
-Have (no) difficulty in sth/doing sth: (no) difficulty in doing something
-Prepare for sb/sth: prepare for someone or something