ok heres the skinny you need first to configure the input/output for the sides you want to use to transfer in and out of your me system then put an import bus on the output side of the furnace and an export bus on the input side of the furnace then configure each to input and output the items you want smelted. optionally you can use a interface to input items into it however you will need an encoded pattern for this to work and then in your me terminal you can click craft and it will send the item in to be smelted check the wiki and or youtube for further info on this
hope this helped