Mobile devices from Apple are not supported...
Left click / tap and hold on untouched cell = reveal cell
Right click / tap on untouched cell = toggle flag in cell
Right click / tap on revealed cell = reveal surrounding cells if feasible
In multimine mode, there might be multiple (6 max) mines in a single cell. Use right click or short tap to increase flag count, left click or long tap to decrease flag count. To finish a multimine game, you have to flag all cells with mines correctly and click the "I'm ready, dismantle the mines!" button.