Your request is very general and has absolutely no details.
I suggest you that you start by searching this site and google for LabVIEW tutorials. Here, here, here, here and here are a few you can start with and here are some tutorial videos. You can also contact your local NI office and join one of their courses. In addition, I suggest you read the LabVIEW style guide and the LabVIEW user manual (Help>>Search the LabVIEW Bookshelf).
After you've learned this and know exactly what you want to do (hardware, software requirements), you can try searching for "EEG" and see if anyone has done anything that can help you.
My project is about designing a system to measure the brain waves and show the signals in computer software. Our system consists of electrodes, amplifier and uses DAQ to see signals in pc. Our expectation is to present the EEG alpha and theta waves.
First, be sure your amplifiers are properly rated and isolated for safety of the experimental subjects.
I have worked on some neuroscience projects involving theta. Our theta detector (LV5.1) consisted of low pass filtering the EEG at 25 Hz and then taking FFT on a sliding window of the data. When the ratio of the energy in the theta band (~3-7 Hz if I recall correctly) to the energy outside the band exceeded a threshold, we decided theta was present. Today I would probably use the Point by Point FFT to simplify the program a bit.
I have briefly looked at curve fitting to detect theta in smaller samples, but have not worked out all the bugs.