Engine oil chamber like

Diagnosing an oil leak can be tricky. If it's been leaking for a while, there's probably oil everywhere, making it difficult to track down the source. The cooling fans and the action of the wind as you drive can scatter it everywhere. it usually helps to clean off as much of the excess oil you can so you can tell when there's new oil on the engine.

Take a large box, unfold it and place it under the engine overnight. Oil drips on it will be much easier to see, especially if your driveway, garage or street is already covered with oil stains from the leak.

Keep in mind that oil follows gravity, so start wherever you see oil dripping on the ground and find the point it's dripping from. From there, you'll have to follow it back to its source, which can be any number of places. If you've had an oil change recently and it started after that, there's a clue right there that you should check the oil filter and the drain plug in the oil pan.

Otherwise you may have to get out your flashlight, remove parts, and/or use mirrors to figure out where it's coming from. It can be a challenge, especially if it's coming from a place that's difficult to get to like the rear main seal. But it's almost always going to be coming from a seal or a gasket that's failed, so you'll want to check anything that's meant to keep the oil in the engine. That could include the crankshaft front seal, the camshaft seals, the head gasket, if you have a distributor, there's a gasket and o-rings there, etc.

Without knowing what year your Altima is, it's hard to give you specific information, so please add that to your question or post it in a comment.