WSO2 Governance registry (WSO2GREG) is a metadata repository. It supports storing, cataloging, indexing, managing and governing your enterprise metadata related to any kind of asset.
Uploading files directly in to the GREG is not recommended. What is recommended is to upload the files in to a file server and use a link to the file as a metadata.
But there may be situations where you really need to keep the files in GREG itself. Let's see how you can do this in GREG.
1. Download the file.rxt file from .
2. Create a new artifact type from the WSO2GREG management console. Extensions-> Configure->Artifact Types->Add new Artifact
3. Download the "file" extension from 
4. Copy the "file" directory to "[GREG_HOME]/repository/deployment/server/jaggeryapps/publisher/extensions/assets/"
This will add a new item "file" in to the menu and you should be able to upload and download files in WSO2GREG.
If you need to make any association to "files" you upload here, you have to do the following to list the files in the associations view.
Let's assume you want link these files to "soapservice" artifact. Then do the following.
1. Edit the Association types for "soapservice" in [GREG_HOME]/repository/conf/governance.xml file to have the file details
Following is a sample configuration for Association type="soapservice", once you add the "file" type