Tightening the belt is a good idea - but you need to get the right one!
That "first big belt" runs the alternator and doesn't touch the power
steering.
You would need to remove the tire and wheel to access the power
steering belt.
Not quite sure I remember just how I tensioned that belt. I think it
was loosening the adjustment bolt and then prying against it in the
adjustment slot.
Use the manual for specified tension - IIRC it was around 80 lbs.
According to Toyota, belt tension is something to be checked
periodically as a maintenance procedure, so definitely try that first.
If you find the working surface of the belt is cracked or glazed, would
be a good idea to replace it.
I always prefer the factory parts - even for belts.
Just bought a belt for the water pump on my truck from Toyota, and it
is very solidly constructed and thoroughly reinforced compared to the
notched aftermarket belt that had been there.