The reflow oven is used for binding solder paste to a PCB. if your PCB came with a stencil, you will probably use the oven for soldering.

Basic Use

Make sure the PCB you are assembling has solder paste applied in the correct areas and there are no shorts. Make sure all the parts are on the board.
Insert the board into the reflow oven. It should be located on the center of the oven.
Turn on the reflow oven (there is a big red switch on the back).
Press the ON/OFF button on the front panel, then press RUN. The oven will do its job. This will take a few minutes. The progress is shown on the LCD display at the front of the oven.
The oven will beep once it's finished, and it will show the message "SOLDER DONE" on the display. The oven can be opened at this point to remove the PCB.
Turn off the reflow oven (with the switch at the back).

Tips

Don't place items directly on the metal rack, raise them with pieces of unused PCBs.
Place only one PCB in the oven at a time.

Heat distribution across the board will not be even - the solder may not bind well in certain areas of a PCB.