Since crDroid recovery does not typically support MTP or OTG, you will use ADB sideload.
This is common when flashing GApps. You can usually select "Install anyway" if you trust the source. If you'd like to proceed, tell me: crdroid recoveryimg install
fastboot flash recovery recovery.img
If your commands executed correctly, your device will boot into the minimalist, purple-themed . Since crDroid recovery does not typically support MTP
adb sideload crdroid.zip