Scraping from a .asp page using POST

I'm attempting to use PowerBI to pull regular updates of posts from a government website:

https://elibrary.ferc.gov/idmws/search/fercadvsearch.asp

This is the search form. It uses a POST method, and I'd like to input a variable into:

<INPUT TYPE="textbox" NAME="textsearch" SIZE=50> 

And then post to the results page:

<FORM NAME="search" ACTION="advResults.asp" METHOD="POST">

This site is public, so I don't think there should be permissions problems. But I'm having a hard time getting it to work. Any ideas on how to pass a particular textsearch variable (like a company name) through the form so I can then download and view recent postings about it? Thanks much.