Before cleaning make sure you have unplugged your kettle and let it cool down. Wipe with a damp cloth, then dry. Do not use abrasives because they will scratch the metal and plastic surfaces. Even though your kettle comes with a filter, you still need to clean the inside (and the filter) regularly. Remove the filter by holding the tab and then lifting the filter out.
Regular descaling of the flat element will improve the performance of your kettle. Supermarket proprietary descalers or vinegar can be used to descale your kettle.