You can sync files that have been uploaded to a channel to your OneDrive storage. When the current files in the channel are updated, or new files are uploaded to the channel, these files will be synced automatically to your OneDrive.
Open the channel that has files you want to sync with. Click the Files tab at the top. On the toolbar at the top of this tab, click Sync. A panel will open that will take you through the steps of signing in to your OneDrive (or OneDrive for Business) account and then setting it to sync with this channel.