I've tried to use cm recovery to flash the Gapps package, but it can't find the zip. I get an error "invalid argument" I have tried flashing through ADB also, but once in recovery mode, the pc can no longer see the device ( nexus 6)
Best way: First, install TWRP because CWM doesn't support it, then wipe data and cache. Be sure to take a backup. Now install CM13 and GApps. Reboot and it will work smoothly.