Cut triangle-shaped MDF blocks for attaching metal adjustable feet. Measure from the floor to the bottom of the radiator fins. Measure the height of the radiator's feet. Subtract the first measurement from the second. The remainder is the distance from the bottom of the cover to the underside of the blocks. Place the blocks inside the front corners of the cover. Drill pilot holes, then glue and screw the blocks through the cover's sides and front. Next, screw the feet to the blocks.
Set the cover over the radiator and adjust the feet to level it. Use a scribe to transfer the contours of the wall's baseboard to the cover's sides. Cut along these lines with a jigsaw to create a tight fit over the baseboard.