Hello, I'm trying to find out what this part location name is, and how to remedy the leak. I have attached a photo of a random engine to show the location / part and hope to find out where in the service manual, or what parts or how to fix the leak.
in this image, it's the black cover behind the fan.

That is the chain tensioner access cover. There is no separate part number for a gasket indicated for my '02 Pathfinder so, since I have never removed mine, I can only assume the cover comes with a gasket or it is sealed with high-temp RTV silicone sealant. I'm betting it's sealant that is required, like so many of the other items housing the timing chain. Unbolt it, take it off, and see for yourself. Have a tube of RTV sealant ready. Wipe off the oil from the mating surfaces, apply a bead of sealant to the cover, and put it back together. Be sure to let the sealant cure before starting the engine. Good luck.

Yep, oil resistant RTV for the access cover. Permatex ultra black comes to mind.

However, if the cover has never been replaced, the leak will almost certainly be caused by the small sensor just above the cover- the cause is a small o-ring around the sensor that has hardened. Disconnect the electrical wire and remove one 10mm bolt to remove the sensor.

If the cover has not been removed, don't remove it to "take a look," as it won't be a walk in the park to get in that tight space. Confirm that the leak isn't coming from that sensor first.