Chose PPTP if you ONLY care about SPEED. PPTP is the Fastest protocol in china. You might face disconnections, if it was the case, please try other protocols, such as L2TP or SSTP.
Chose L2TP if you are facing frequent Disconnection. L2TP is slower than PPTP protocol in china. You might still face few disconnections from time to time, but it will be much less than PPTP.
Download the Software to use PPTP on Windows. After download, extract the file, and save it. Run the software and input your username and password to start using the VPN.