You should be able to feel rubber or silcone grommets on the floorboard bottoms. These are attached to the bottom of your Ness boards. Push up on the grommets while pulling up on the Ness boards. There are a few so you'll have to repeat until the boards are loose.
To reinstall put the boards in place and look through the bottoms to make sure the grommets are lined up. Press on the boards and either work a small screwdriver around the grommets until they are all the way through or use a small pair of pliers to carefully pull them through.
Retired USAF, IYAAYAS!
2008 V-Star 1100 Custom Bobber project
2011 Crimson XR with Forged Highway Bars / Hard Bags / Passenger Backrest, Ness parts including Smooth Layback Plate Frame/Mount / Rad 3 Mirror / deep cut grips / drivers floorboards /shifter peg / brake peg / passenger pegs. Witchdoctor black rack, Lloydz filter / timing wheel / VFC III, 7Jurock windshield, Drag Specialties seat.