where do I add oil to the front axle or where is the fill plug located?

Fill plug is on top of differential its very tight access suggest having a shop check and fill if needed. The 4wd light is not on due to low fluid level the 4wd light is indicating an electrical component in the 4wd system is malfunctioning.

Hello, The 4 wheel drive icon flashing will not be related to fluid level typically. The manual does not describe the location, but safe to say it's on the housing of the differential. Just have a thorough look.