Lubricating bifold doors is the solution when things are sticking or making noise. Just like other door hardware the hinges can start to squeak. A little oil can do a lot of good on a troublesome door.
The hinges, rollers and pivot pins are the moving parts. Use a good quality silicone lubricant. Keep a rag handy and don't over do it. Work the door panels back and forth until the move freely and don't make noise. Watch for drips and clean them up with the rag. Lubricating bifold doors move is not rocket science and you should be able to focus on the spots that are causing problems.
You may need to work the door back and forth a few times after you oil it. Keep a rag handy for the oil that oozes out. While you are at it, check all the moving parts on the door. Add some oil gingerly and you won't have to do this again for a while. That's all there is to lubricating bifold doors.