With that ribbon cable and the clasp, you need to pull it back to unlock it, then once the cable is inserted you need to push it back into place to hold the cable securely.
All of the mounting hardware for the Argon case will be in an anti static bag that comes with the case, there will be 6 in total, 2 countersunk screws for the inside of the case and 4 dome head screws as well as 4 rubber feet for the outside of the case.
If you didn’t receive those with your order, please email us at support@coreelectronics.com.au with your order number and we will look into this further with you there.
The easiest place to find your order number would be to find it in the order confirmation email you would have received when you placed the order for these parts.
If it helps you find it, the order number usually looks something like this: 1000123456
You can either connect the Pi directly to your router via an ethernet cable, otherwise you would need to input your WiFi credentials into the network manager, by default it is displayed on the top right of your screen on the task bar.