If you don't see anywhere to put any oil then it probably has ball bearings and uses grease. You may need to take it apart to re-pack the bearings. The good news is it doesn't need done very often. If it only sees light use you can go for years.
It may even have sealed bearings. The grease in those is good for about 20 years then it dries out and you replace the bearings.
Rodney