Welcome to the site from Central California!!
With the engine off, remove the reservoir cap, wipe the dipstick off then momentarily reinstall the cap. Remove the cap again and check the fluid level. Add power steering fluid as necessary, but be careful not to overfill - the reservoir fills up quickly. Add fluid in stages, a little bit at a time while rechecking the level, until it's between the ADD and FULL marks. Don't add all the way to FULL, because the fluid will expand as it warms up.
Install the cap, start the engine and crank the steering wheel lock-to-lock 2 - 3 times. Shut the engine off and recheck the fluid level. If the fluid is foamy, let the vehicle sit for ~15 minutes then recheck the level - add as needed and repeat the process until the fluid level registers FULL on the dipstick, the fluid is not foamy, and the steering no longer growls as you turn the wheel back-and-forth.
Steering fluid dripping off the rear axle would represent one heck of a leak - the entire bottom of the truck would be saturated with steering fluid. Unless that's the case, the leak at the rear axle is a separate issue. Once you have filled the steering reservoir, have someone start the engine and cycle the steering wheel back-and-forth while you watch for fluid leaks from the pump, the hoses, and the steering gear.
1
