PSAT 8/9 Help Needed

Hi everyone, 

I will be soon taking the PSAT 8/9 as an 8th grader next week, but I don't really know where to study. I have finished all the College Board Bluebook practice tests, and Khan Academy doesn't have official PSAT 8/9 stuff. I don't know why I am still scoring so low, as my goal is 1400+ but even after so much practice I am only scoring a 1170. 

Thank you in advance!