For Mouse: MS001, MS002, MV021 

USB Type B Pairing Tutorial

For Keyboard and Mouse Combo: KUS009, KUS015, KUS015E, KUT019, KUT027, KM033, KM034

USB Type M Pairing Tutorial

For combo: KUS045
Under 2.4G Wireless channel, hold left button + right button + mid wheel down for 3 seconds, and insert USB dongle to pair.

USB Type E Pairing Tutorial

For Mouse: MV009 MV015 MV016
Hold right button + mid wheel down for 3 seconds and insert USB dongle to pair.