Remove the mask by pulling it off from behind. Use the back strips to avoid dragging the mask across your forehead.
Remove the filter and dispose of it immediately. Used filters should be disposed of in a closed container (e.g. plastic bag) and insulated to prevent contamination. Once you have removed your mask and filter, avoid contact between the filter and your face or hands to avoid contaminating yourself.
Wash your hands thoroughly with soap and water or disinfect them with antiseptic gel.
You can see how to do it step by step here.