free online backup? Of any step in this process choosing your files is probably the most cumbersome. You have to choose which files and folders you want included in your backup set. You want to ensure you take your time at this point because there’s nothing worse then realizing something wasn’t backed up if you do have a crash.
Usually if you choose to backup a single folder then all the other sub folders and files will be included. Be sure to double check that and not just assume that all the files within a single folder have been selected.