The ribbon connection is generally done with a pinch bar that has to slide and lock to make sure the connection is good (at least with the ones I"ve worked on). The ribbon cable must be fully seated into the connection and if the pinch bar has been seated properly, a light pull with your fingertip (just enough to tell if it's secure, which is not much at all) will tell you.
I will also suggest doing some internet searches for How to replace a keyboard on your specific model laptop. It may provide some picture and instructions that would be more product specific for you, sacuh as this one:
http/repair4laptop.org/disassembly_acer.html
And I will presume you made sure you receive the correct model keyboard (part numbers match the one being replaced).