Since the board and schematic files are linked, you can use one to find parts in the other. For example, where on the Circuit Playground Express is the accelerometer? It's pretty easy to find on the schematic, there's a big label that says "Accelerometer". Here's how you can use that to find the part on the board.
In the schematic window, click the eyeball icon (Show).
Then click on the accelerometer part in the schematic.
The part will highlight in both the schematic and board views.
This can be done in either direction, schematic->board or board->schematic. Even though highlighted, the part can sometimes still be hard to find on a busy board. Try turning off layers to help clean up the view.