I'm a bit worried that you're in deep here. How exactly did this problem come about? Is this a class assignment? Is it possible you have misunderstood what you are supposed to do?
It could be that you have been assigned to send some complex numbers from one URSP to another, but I strongly suspect that this "file of complex numbers" is in fact a complex baseband waveform (which is represented by a series of complex numbers) that you have been asked to feed into the USRP in order to modulate to an RF carrier, and then examine on the other side of the link using another USRP. If the previous sentence sounds like a foreign language to you, you should talk to the TA or professor supervising your course as you likely need to come up to speed on some basic concepts.
If your actual goal is to "play back" a complex baseband waveform, the easiest way will likely be to use GNURadio. You will need to somehow interpret the numbers in the file as complex samples that GNURadio can understand - there are many ways to achieve this. Probably the easiest would be to write a Python script to convert the file into the simple binary format that GNURadio understands. Once you have them into GNURadio, you'll need to do sample rate conversion (as applicable) and then pipe the stream into a UHD sink. The UHD driver will deal with the rest.
If instead your goal is to faithfully transmit a list of complex numbers from one lab station to another using USRPs, you are basically discussing creating a full modem system. This is much more complex task, and is beyond the scope of what one can answer in a simple StackExchange post. See here for a basic demodulator tutorial from the GNURadio wiki. It's a non-trivial problem. I would recommend picking up a good textbook on digital communications theory, and talking to your course supervisor.