Back the lower plate away from the upper plate using the wrench. Check that the wrench is seated well before knocking it with a hammer - the nub on the end of the spanner wrench that fits in the hole on the plate can break off.
If it has been a while since they were adjusted, spray some PB Blaster first.
If these are new, you should be able to easily rotate the lower plate with the wrench without having to knock it with a hammer. Once the two plates are no longer in contact, the one that is in contact with the spring will rotate but takes effort. It helps if you remove the sway bar link to get more space to swing the wrench
I made the mistake of going the wrong direction when I did mine - it was late at night and I wasn't thinking straight. If you rotate the plates so that you are compressing the spring (plates moving up - towards the top of the car- when installed), that creates more lift.