This video shows how to replace a standard UK single domestic socket with a double socket. Single sockets are often not suitable for today’s power hungry households which mean that some people buy unsafe adaptors that put undue stress on the sockets, if such a device is banged when someone is walking past it can mean that the socket is damaged so badly that it is possible to make contact with the live terminals inside. It is therefore much safer to change the single socket for a double, this is very easy if the socket is installed in drywall, but a bit more difficult and time consuming if the wall is solid. If you have a solid wall this video might help- https://www.youtube.com/watch?v=oso7NWPOFyE
Obviously if you have no electrical experience then you are better off getting an approved electrician to change the socket over for you.