Final answer:
Dashes are used in the given sentence to show the character's stuttering. The correct placement is between the repeated 'I'm' before the phrase 'hooked on phonics'.
Step-by-step explanation:
The dashes should be placed in the dialogue where the speaker stutters or where there are interruptions in speech. In the sentence provided, "I called the Addict Hotline," divulged Kirby, "and I had to admit that I'm I'm I'm hooked on phonics!", the dashes are used to indicate Kirby's stuttering as he repeats 'I'm' before stating 'hooked on phonics'.