How can I free up my upload space

I have a free account and want to know how i can free up my upload space because it is almost full.  I have deleted all my submissions but still the upload space is the same.  

Apologies for the inconveniences caused. 

Deleting the submissions where you've received files is indeed the way to clear up the upload space, I've recalculated your usage and it was decreased now, kindly check and let us know if you have questions. 

Thanks.