The top part is the minecart itself, the bottom part is the inside of the minecart (so you don't see the ugly white)

1. Cut out the model
2. Fold along the dotted lines on the cart and fold the tabs
3. Glue the model together

Optional: After step 1, you can cut the inside cover and glue it on the other side, make sure you only glue the faces in the middle, so you can insert the tabs and add more glue to fix it.

If there are any problems with the model, write in the comment box!