Update: 2018-05-31 Preview：1842 For:AC10U 、
Model Number: Tenda AC10U
Question Classification: Function Setting
Step 1: Open a browser and type tendawifi.com in Address Bar, tap “Enter”. Input login password and tap “Login”.
Step 2: Tap “VPN”. and choose “PPTP/L2TP Client”.
Step 3: Enter correct VPN information and tap “Connect”.
Step 4: If connect successfully, you can see “Connected” in connection status.
Will it help you?