Fan has black, blue, white, and green wires. In the outlet box there are 2 black wires and 2 white wires. How do I wire this?

One of the cables (one black and one white wire) is hot. The other goes to the switch. You must determine which is hot and which goes to the switch.

You do that with a meter.

If you do not have a meter, temporarily hang the fan and connect the black and white of the fan to the black and white of one cable.

Turn the power on and see if the fan works. Don't forget to work the fan pull chain. If the fan works you have connected the fan to the hot cable. If the fan does not work you have connected it to the switch cable.

Connect the black of the hot cable to the black of the fan and to the white of the cable going to the switch. Connect the white of the hot cable to the white of the fan. Connect the black of the switch cable to the blue of the fan.

Connect all grounds together.