The CW only keeps a few recent episodes of Arrow on its app. Even though Arrow is a CW show, the broadcasting company has signed off the show’s rights to Netflix to offer the show to viewers exclusively. While you can catch a few episodes on the CW app, most episodes are missing. The ads won’t provide a good watching experience anyway. It’s best to watch online via Netflix US, which you can unblock with a VPN or SmartDNS on your streaming devices.