You can only edit paths that were made by yourself. Luckily, there’s something else you can do -- duplicate an existing path. If you duplicate a path, a replica of that path will appear and and you will be the author. NOW you can edit that and add new content if you want to!
Keep in mind that an admin can edit all paths, whether they are created by other users or not. Learning paths created by Crammut can’t be edited.