Follow the instructions relevant to your situation:
The LIFX app should recognise the lights still! You don’t have to do anything if this is the scenario.
Schedules and scenes will still work with the lights once reconnected. If you use the same light names, all other integrations should work as expected as well.
For express support and step by step instructions, please go to: https://lifx.typeform.com/to/fQ9I3W