Did you remove the wash arm? If so the cover will just lift off. If not the center of your lower wash arm has a small disk so to speak.While holding the wash arm stationary,unscrew that & the wash arm will come off. I use white vinegar (1 cup every 2 weeks to keep it clean.Wait for the first fill & hear it washing then open door & dump in.) Make sure you clean the 4 slots in the wash arm support.That is what keeps the filter clean.