I would encourage you to purchase the Control Design Toolkit. It features many different graphical tools to design and analyze control systems. There are multiple examples on our website as well. Just search for Bode plots. Otherwise feel free to consult Chapter 7 of the CD Toolkit manual which talks about Bode plots.
Without the Control Design Toolkit, you would need to create your own Bode plot algorithms in LabVIEW. The document that Kalin linked should be helpful for that. I don't know of any free software that replaces the Control Design Toolkit. You mentioned that you had already started programming, but you didn't say which VIs you are using. Let me know what you have done so far, and I may be able to help.
Do these toolkits, Control Design orSound & Vibration Analysis, provide for hardware in the loop (control DAQmx hardware to generate stimulus waveforms and collect response waveforms) ? I don't see anything in chapter 7 that mentions hardware.