Here, we have a molecule formed by two elements:
Sodium, Na
Cl, Chlorine
In the periodic table, you can locate the elements and there you will find the molar mass of each one.
You also can find with the name of atomic weight
So, Na is located on the group IA and has an atomic weight of 22.99 g/mol
Cl is located on group VIIA and has an atomic weight of 35.45 g/mol
Now, to have the molar mass you need to sum both weights:
22.99+35.45 =58.44 g/mol
So, the molar mass of NaCl is 58.44 g/mol