Valmiki Ramayana Sundara Kanda Sarga 58 Shloka 137

मया च I also, वालिनः Vali, वधं प्रति will kill in turn, तस्मै your, कथितम् story, तत्र thereupon, मे to me, सहाय्यहेतोः will help, समयम् agreement, कर्तुम् will do (said), अर्हसि is proper.

'Sugriva told the story of Vali in turn and asked for his help and to make agreement to kill Vali.