I have some of those brackets. In the picture, the bracket is sitting upside down, pick it up and turn it 180 degrees so the lever that moves is on the top. Mount it to the wall that way.
In the right picture, take the thing that moves and move it to the left so that the longest part is parallel with the left side of the mounting bracket using the right picture as reference.
Take the blind and push it up tight to the bracket and spin that moveable arm 90 degrees. Those 2 slightly raised tabs and that slightly raised tab on the moveable arm fit into the 2 curved pieces at the top of the blind support using the bottom picture as reference.
Once you spin that moveable arm, those raised tabs will now hold the blind in place. They are a pain in butt to use but they are what you have.
Do a "dry run" with the blind sitting where it is and try to fit the bracket into that top channel. Remember to move that moveable arm to the left in the picture before you try to mount that bracket so the tabs (3) are on the same side. Then fit the bracket to the blind and move the movable arm about 90 degrees so it's tab is forced under the opposite lip.
Try it a few times you will understand how it works. When hung correctly, the curved tops of the blind sits on those 3 tabs. (2 tabs in the front and the moveable tab in the back). When you are mounting the blind, that moveable arm will be sticking straight out, stick the blind over those 2 front tabs, push the blind up tight into the bracket and lock it in place with the tab on the moveable arm.
Job done. hope this helps.