Your friend wants to know the amount of salt added to her favorite fast food french fries. what would you recommend that she do to find out the amount of salt ?

Every fast-food chain is required by law to make the nutrition content of the
items on its menu publicly available.

My friend should walk into her favorite place, or into the nearest McRonald's,
Bendy's, Tennessee Fried Turkey, Bulgur King, Plucky Please, White Palace,
Pita Hut, Carl's Senior, Back in the Box, or any of those others, ask to see
the Manager, and ask the manager for a chart of nutritional information that
includes their french fries. 

To be nice about it, she should do this at a time when the place is not too busy,
and the manager doesn't have a lot of more-important things that need to be
done right now.

Under the french fries, look at the serving size, and the figure for "Sodium"
in that serving, which is the nutrient that your body gets from salt.  Less is
better.  More is worse.  For an adult, the CDC Institute of Medicine says
that 1500mg a day is 'adequate' for an adult.  The US Food and Drug
Administration recommends that adults should get 'no more than' 2300mg
in a day. People who have high blood pressure are supposed to watch it,
and take in a lot less sodium. 

And there are organizations with official-sounding names that totally dispute
all of this.

But to answer your question, that's what she should do to learn the amount
of salt used at the place where likes to get her french fries.