Hi Sandy, its a common problem with fondant covered cakes.
Air always gets incorporated when you drape the fondant over the entire cake, its now up to you to eliminate it by
working from the middle of the cake outwards and downwords.
Using your smoother, start to adhere the fondant to the cake from the middle and work outwards gradually till you get to the top edge of the cake. For the cake sides, also adhere the fondant in a circular manner (meaning start at a point and go a complete 360 degrees round, till you arrive at the starting point). This way you keep working gradually downwards, till the entire cake is covered. The aim is to gradually expel any trapped air.