Connect the resistor and LED as shown in the diagram below. Make sure that the longer lead of the LED (the positive lead) is to the left. It doesn't matter which way around the resistor goes.
When connecting the micro:bit to the breadboard, its best to put the alligator clips vertically into the holes on the micro:bit's pads, otherwise the clips can slip off or make accidental connections with neighbouring connectors on the micro:bit.
The way that solderless breadboard works is that behind the holes into which you poke component leads you will find a metal clip.
The red lead that connects pin0 on your micro:bit to row 3 of the breadboard actually connects the lead to every hole position on that row (at least for the left-hand bank of rows of five). The right-hand side of the resistor then connects to the clip underneath row 3 on the right-hand bank and hence to the positive lead of the LED.
The long columns down the sides of the breadboard work differently from the main rows of connections in the central area of the breadboard. Each of these long columns are bade up of a single long clip that is often used to provide power. In this case the right hand column (with a blue line next to it) is connected to the micro:bit's GND connection and also to the negative side of the LED.
The resistor is necessary to limit the current flowing through the LED. A digital output from a micro:bit should not be allowed to draw more than 3mA of current. The 470Ω resistor limits the LED current to under the 3mA limit.