first you should open the txt file, there is a function called something like "read from text file" in the Function palette (I'm not sure if it is exactly named like this in English, I'm using the German LabVIEW version. It should be located in Programming > File I/O).
This function can read each line from the txt file when using a loop and returns the wanted text line as a string. Put then each of the strings read into an array.
The array data with magnitude and angle will be the input for function "polar plot" which displays the plot on the front panel (Programming > Audio&Graphics > Plots > polar plot. You can also open the Function Palette, use the search option and type "polar").
It is also described in the LV Help which data types you need and where to find the functions. Be aware that the polar plot function is not available in the LV Base Edition.