How do I get access to the CD lens

If it's a player that sucks the CD in or takes it in on a tray, then a certain mount of disassembly would be required, but in that case it's unlikely that the lens would get dirty. You can get a lens-cleaning disk but it's not very likely to help.

If it's a player where you have to put the disk on the spindle yourself then you will be able to see the lens - a glass dome a couple of millimeters in diameter.