To reach an optimum ingress protection (IP67) rating and to achieve maximum pull-out resistance :

Ensure that the conduit is cut straight and smooth
Gently pull lock tabs on fitting out to allow easy insertion of conduit into the fitting and observe that the conduit is fully seated inside the fitting and seats well against the integral seal located inside the fitting
When conduit is full seated push the lock tabs back in towards the conduit ensuring that these tabs are both on the same groove of the conduit and then pull the fitting away from the conduit to ensure that the fitting is locked.
Finished assembly
To remove the fitting from the conduit you first must release the pre-load from the fittings lock tabs by firmly pushing the conduit back into the fitting towards the threads and hold it pushed in…. then slide the fittings outer locking collar back towards the threads this will release the lock tabs from the conduit .