Safely and correctly installing a battery

Hi - we are new to this game - we have a BlueRov2 - heavy config.

Looking for a video that shows how to correctly and safely install a LI-4S-18AH-R1 battery.

Currently we are finding the XT90 connector is completely crushed/bent against itself when we go to put the cover back on.

Is this correct or are we doing it incorrectly?

Thank you