You’ll need to inspect (assuming a hydraulic PS system) the following likely culprits:

PS reservoir
PS pump
PS hoses (high pressure and return)

If you find any leaks (obviously) replace those components. If you can’t find any maybe replace them all - not too hard or expensive (relatively speaking)

After you’ve added your PS fluid (often it’s ATF)
MAKE SURE you bleed/burp your system
thoroughly by having the wheels in the air and (engine off initially) moving the steering wheel lock to lock (a ton of times) until there’s no more burps and the fluid is staying level after you’ve added it back up to the correct level.