How to Change Network name on NightHawk

I bought and installed the Extender when my 2.4ghz & 5.0ghz bands were merged.  I have unmerged them and need to know how to set up the two networks on my Extender.  Do I use Factory Reset and start over? I didn't use the Nighthawk App but could use it, however it asks if I'm installing new and I don't know whether to say YES or NO.

Please help!