Stairlift power source (Minivator 930)?

Hi, A stairlift was donated to us and installed by the previous owner. He was not sure where to plug in the power charge to the chair. It worked for 10 times but now needs to be charged. On what part of the lift do we plug these 2 prongs that are on the adapter to plug into the wall. It is just my son and I that need it for my disabled husband. A diagram would be awesome and unable to find one on the internet. Thank You