This tutorial will explain how to download CM and install it on your Oppo N1 Android phone. Before you proceed, make backup of anything important you have on your phone. After you done with that, make sure you have TWRP as your recovery. Stock recovery would not work.
Second, it is important to be on stock ROM. It does not matter if you are rooted or not. Now, download the fully flash able ZIP from here. Put it on your SD card and reboot to recovery and flash the ZIP from there.
You are not done yet. Reboot into TWRP and go to Advanced Wipe -> Wipe Dalvik Cache, Cache, and Data.