You may have files either stored on your PC or with another Cloud Storage provider.  You can move these into WorkDrive.

If you've downloaded WorkDrive TrueSync your WorkDrive will appear in File Explorer.  Form there you can just drag and drop files or folders from their existing location to WorkDrive.  If you've not got your other Cloud storage syncing with your files, just go into the web version and select the files you want to add to your WorkDrive and download these.  Once they are downloaded, go to the location in File Explorer where you've downloaded them to, if they've go to a Zip Folder, go to Extract All and choose your WorkDrive Folder as the destination folder.

If you've accessing WorkDrive in a browser,  you can just drag and drop files or folders from their existing location to WorkDrive.  If you've not got your other Cloud storage syncing with your files, just go into the web version and select the files you want to add to your WorkDrive and download these.  Once they are downloaded, extract all files from the Zip Folder, save the files to a temporary location on your PC and then just drag the files into WorkDrive.