What do you mean by "generate"?
If you just need 5V for an external circuit (and don't need to control the voltage), there is a 5V, 200mA max supply available on the USB-6008 terminals. This is on constantly. Just connect to it and to a ground terminal.
If you have to control the voltage, there are several choices, depending on your requirements.
You will have to know how much current you need to supply, as well as the minimum voltage you can use to power your circuit.
If you just need to turn it on or off, and require relatively little current, you can use a digital output. These are open-drain outputs that have a 4.7K resistor to the 5V supply. So if you can use anything over (say) 4.7V, then you can power a circuit that takes up to (5-4.7)/4700 = 64µA. Just turn the output OFF to turn your external circuit ON.
If you just need to turn it on or off, but you need more than that relatively small amount of current, you can use a digital output to control a p-channel FET: connect the source of the FET to the +5V power terminal on the USB-6008, the gate of the FET to a digital output, and the drain of the FET to your load (with the return from your load connected to the ground terminal on the USB-6008, of course).
If you have to control the voltage to something other than "ON" or "OFF", you could use an analog output. As described in the User Guide for the USB-6008/6009, there are certain
limitations to the drive capability of the analog outputs. They are capable of providing up to 5mA, but they have a 50Ω output impedance, which means that if you try to get 5mA out of them, they will droop from +5V down to (5 - (0.005 * 50)) = 4.75V.
If you have to have control AND high current AND require a full 5V, you will have to use an external supply and an external transistor or other buffer to increase the output capability of the analog outputs.
