How can I use Explorer in Powershell to select a file to be processed within my Powershell script

Question

I wrote a script in which I use a static file for example "datainput.csv"

I would like to launch an explorer session within my script to allow the user to pick a file and then be able to grab the file name within the script to process it.

I have no clue where to start..

I know how to launch Explorer, but not grab the file name.. Right now explorer launches the file external to my script.