Assuming that you mean version 10.1.2.<something> when you say "...using Forms Developer 10 ...", you can use WebUtil to do this. Information about WebUtil is include in the Forms Builder online help. The Forms WebUtil demo can also be helpful as it includes examples of uploading/downloading. Keep in mind that this is a "demo". Questions or concerns about this demo should be posted here, in the forum and not to Support as they can only offer limited assistance with demo/example code.
For more information like installation/configuration details, refer to the following MyOracleSupport note:
<blockquote>How To Install Webutil on 10.1.2.x Oracle Application Server (Doc ID 566628.1)</blockquote>