Importing xls into P6

Hi,

Recently I have been experimenting with importing xls into P6. 

I have managed to work out how to use this to update already created activities within the programme, however when I try to introduce new milestones within the xls and import back into the programme no matter what i try they always appear as task dependant and sit on the data date. 

Is it possible to create milestones outside of the programme as im trying, and if so can i have some help on how to.

Thanks in advance.