Undo the bolts on the side of the stem. Undo the top bolt in the cap a little until there is a little fore and aft play when you hold the top and bottom of the fork and rock it. If not undo until there is, just a little at a time mind. When you have play it's a little too loose so gently tighten again @1/4 turn at a time until play is just eliminated. When you reach that point tighten the stem bolts, That should do it. Greasing requires that you dismantle the entire headset and rebuild in the correct order, cleaning and greasing as you go, perhaps best left alone for now.