To configure the VPN-connection on iOS for iPhone, you must perform the following steps.
First, open "Settings" in the main menu:
In the window that opens, depending on the version of the OS select "Network" and then click "VPN", or at once, select "VPN":
Choose "Add VPN configuration":
In the new window, you should go to the tab "PPTP", where you need to enter the IP of the server(List with IP addresses of servers for PPTP connection), your login and password on the site. Then set "Send All Traffic" in position "ON". Then you need to save your changes by clicking on the top right button "Save":
Then, go back to the previous menu and check the status of your VPN-connection.