Please pause the printing, then slide the switch to retract gear, use hand to pull up the filament. Precaution: please do this before all the filament goes into the feeding hole or there will be no filament hand can pull up).Then put new filament into the hole and use another hand to slide the switch to feed gear, wait about 10 seconds till the filament come down. Then slide switch to the middle gear and press printing button shortly to resume printing. Please pay special attention that ,after feeding 10 seconds, timely slide switch to the middle gear in avoid that the filament pimple appear in the model.