Ikea Faktum kitchen one side panel - Perfect abstract high gloss white

Hello everyone

Yesterday I bought Faktum kitchen units. The Ikea planner put together two base cabinets for us with an end panel that was supposed to be attached at the back. But now our problem is that the back has a thin back panel (standard back panel). How do you attach the end panel to this back panel, can someone help me? There are no instructions for this.

Hello My question: Why on the back wall - the element stands free in the room - I solved similar with gluing! Best regards bergpriv :)