Click Reply,
Additional Options,
then browse to your local files and click the one you want to attach.
Once the schematic is started, connections there will show up as 'airwires' on the board that need to be connected.
You can run Error Check on the schematic, it will warn you of unconnected pins & stuff.
Use the 'abc' button to name signals "+5V" and "GND", or other names.
Once everything is named it is much easier to follow routing on the board.
You can run Design Rule Check on the board for similar; unconnected, overlapping signals, etc.