I see what's going on. You are trying to mount seperately and that doesn't work. With the kraken came some longer 6/32 screws. With the case came some short fat stubby thick screws for mounting the fans.
What needs to happen is you remove the short fat screws, and the long thin screws go back in those same holes, through the fans and into the radiator holes, sandwiching the fans between the radiator and case.
It's a little bit of a pain, but that's how it's done. If worried about the fans falling out of place, you can leave the bottom 2 screws on each fan, and just use the top holes of each fan for the long screws. 4x screws is plenty of support to start with and once those are in and snug, then swap the 4 remaining screws out.
My kraken came with 16 long screws, 8 being just a few threads longer than the other 8. You'd want to use the longest 8 to go through case-push fan-rad. The remaining 8 long screws are for use in the rear of the rad, going through the pull fans.