To manually set up an L2TP-or-PPTP connection under Windows 10, read the instructions as followed.

At first, you'll need to bring up the Settings window and enter Network & Internet.

After entering Network & Internet, you'll need to click VPN, and select Add a VPN connection.

At first, you'll need to obtain the server address you'd like to use and your preshared key.
You can do this by signing into your account and accessing the page in the image below.

Go ahead and fill in the information like so. For the server name we recommend using the IP address if you are on a very restrictive network.

After that, you'll need to head over to Adapter Settings and edit the properties of the profile you created.

Change everything in this window under security to match what's in the image below.

After this, click on Advanced Settings and make the changes as shown here.

To disable IPv6, close out of Advanced Settings, and go to Networking.

After this you can go ahead and close the Window. We're now ready to connect.

Go back to Settings > VPN and click Connect.

Congradulations, you've successfully setup and connected to L2TP under Windows 10.

Thanks for checking out this guide. Feel free to contact support if you have any trouble.