"Says" is present tense. "Said" is past tense. If someone had said something in the past, but it may or may not apply now, you use "said".
For example:
"She said that it's better to take the test with a pencil instead of a pen."
If they said something recently, and know they still believe something to be true (if they would say the same thing again), you use "says".
Example:
"She says that it's better to take the test with a pencil instead of a pen."
Hope this helps!