1. You need to contact o2 on the phone either 202 or 0344 809 0202
2. If you need to send the phone away it will be around 7 days to get it back to you,
3. The excess is based on your premium and how quick it needs to be exchanged full details are here: Phone Insurance | Insure Your Mobile For Damage Cover | O2
Just to make you aware you may get a refurbished handset and not a brand new one, and it may come in a plain box.
Most likely O2 insure will send a replacement phone and collect your damaged one at the same time.