Machine Configuration
Certain blocks may be configurable, this means you can change where the block's inputs and outputs are located. To access a block's configuration click on the cogwheel in the top-right of the block's gui.
In the config you will see 6 tiles each representing one side of the block. Hovering over a tile you tell you what side it is and whether it is an input, output, rejection output or if it is not used at all. A rejection output is where an item will go if it was rejected by the block. For an example an oak log would be rejected if it was put into a currency converter, as an oak log is not a form of currency.
You can cycle what a side of the block is used for by clicking on the tile which represents that side.