For using xDrip+ with data coming from your Nightscout site, you only need to enter your site URL, you can also download compatible treatments from Nightscout (BG, calibrations, treatments).
With a classic DIY Nightscout URL it will look like this:
If you use a hosted service contact the vendor for more information.
If your Nightscout site is secured, you need to add the API_SECRET or a token information.
xDrip+ performs limited (24 hours) data backfilling from Nightscout.
You can receive data from Diabox by enabling http broadcast in the app and making xDrip+ a local follower.
You cannot use this feature with xDrip+ running a web service.
Once done set xDrip+ in Nightscout follower (see above) with the address: