Depending on your plan, the default storage you have on your account may vary. You can increase it anytime in the following manner:
Click the Account Settings button on the left sidebar
Proceed to Billing
Here you can see your current storage capacity and how much you have already used. Click Manage Storage
4. Choose a package and click Add storage.
Note: The cost of the packages is the following: $9.95/Month for 5GB and $29.95/Month for 20GB.
There you are! You'll be redirected to the checkout page.