As the workspace owner, you can change the file ownership by going into file properties and changing the ownership there. Otherwise, if you are not the workspace owner, you can get one of your business administrators to give you ownership of the workspace or get the owner of the workspace to transfer ownership to you.
To do this as a workspace owner:
1. Right click on the file
2. Select "properties" at the bottom
3. Scroll down on the dialog that appears to find "Transfer ownership"
4. Select your own user and click OK