Please email the instruction sheet, or detailed installation instructions. I'm not able to view on your site.
To replace the tub ring, on the back of the control panel are 2 screws on the lower outer trim, loosen the screws and lift the bottom of the control panel from the front and roll it up. Once you do this there will be 2 clips holding the back to the cabinet. Once the clips are removed then you can take the cabinet off and expose the tub. The tub ring has clips at the bottom of it that you will release to pull the ring off and put back on.