Sodium chloride contains Na+ and Cl- ions.
This is 1 positive charge and 1 negative charge.
To work out the charges, you can look at sodium and chlorides atomic numbers and draw out the shells. After you've done this, look at the outer shells of both and you will see that Sodium will need to lose 1 electron in order to have a full outer shell and that Chlorine will need to gain 1 electron in order to have a full outer shell which gives u the charges.