LineageOS 14.1 is the custom version based on Android 7.1. Check if your device is officially supported there.
The primary hub for Android development. Look for your device's specific sub-forum. android 7.0 custom rom zip file download
You must have TWRP (Team Win Recovery Project) installed to "flash" the ZIP file. LineageOS 14
Installing a custom ROM typically follows this universal workflow: android 7.0 custom rom zip file download