You can't. The USB-6000 does not have any analog outputs. Perhaps a USB-6001, USB-6002, or USB-6003 will meet your requirements.
can I not use the digital output of USB 600 to control my 5v relay, if so can i please have an example vi which can perform this task.
That would depend on your relay. I see 2 possible issues:
1. The US-6000, when set to Active Driver, only outputs 3.3V.
2. If the current draw from the relay coil is 4mA, the output voltage will be 2.2V.
So you may need to add in a buffer to allow the voltage level and current capacity you need. I have had success with a SN74LVCC4245APWR to do similar.