Bailey Orion awning

We have,as our first caravan an Orion400.2...we have been trying to erect an awning...but the awning rail does not go to the bottom of the van,the last bit is covered by a plastic wrap round cover,we can feed the awning in but cannot get the last bit in because of this cover..we could tease the plastic cover apart and feed it in but this seems not quite right...I'm sure other Orion owners will understand my query!..but any suggestions would be appreciated..thanks...