At the back of the engine theres a container thing and it has marking on it telling you how much fluid is in it.
At the back of the engine bay under the brake fluid container.
The Nissan Altima has an opaque cylinder that holds the brake fluid. Looking on the side of the cylinder, check the high and low marks and make sure that the fluid is between the two.
Everyday
check your brake fluid levels
At the back of the engine there is a container you pour it into.
There should be a container you pour it into in the engine bay.
Somewhere around the gearbox in the engine bay.
Things you need to check is brake fluid oil, and brake pads. If they are fine then it is the brake switch which needs replacing. Also check the handbrakes as sometimes it is left engaged.
Brake fluid level is marginally low, check pad wear rather than just adding fluid.
Check the fluid or posibly the pads are wearing.
check the brake fluid level
Check the fluid level in the master cylinder.