There are two ways to do so:
(1) If your friends are willing to sign up a DriveHQ account, that would be very easy. You simply share a folder with "Full Access" right to your friend using his DriveHQ username or his email address. The shared folder will appear in the "DriveHQ Share" virtual folder when he logs on his own account. He can upload or copy files to the shared folder.
(2) If he doesn't want to sign up a DriveHQ account, then you can easily create a sub-account for him to logon. First, upgrade your account to a Group Account by logging on DriveHQ.com, click on "My Account", then "Group Account". Then use the Group Admin tool to create a sub-account. You can give the username / password of your sub-account to him. When he logs on, he can upload or copy files to the "\DriveHQ Share\SubAccountUserName\GroupWrite" folder.