Hi Sean,
Frank's reference is a good place to start. But also, I note that the format of the data in your notebook is not very useful in Mathematica. There are two issues:

1) The repeated values separated by newlines will generate repeated input resulting in repeated outputs, rather than a list of values. Most probably, you need to import the data, or if inputting it as an input cell it would need to be properly structured as a List in Mathematica. I dealt with this by saving the data as a txt file and then doing an import.

2) There is a notation for scientific format using "^" in place of "E" not recognized by Mathematica. I dealt with this by Importing the data as a String, using StringReplace to change the "^" into "E" so the numbers would be in E format, and then Importing from the String into a data table as a List. (Which I also flattened to a single list.)

Having done this, the imported data can be Fourier transformed easily. To understand the format of the output, and the relationship between sample interval and frequencies, you shoud refer to Frank's suggested link.  I've attached both files.

Best regards,

David