The impeachment process for all federal officials...not simply the president begins in the House of Representatives.
The House Judiciary Committee could pretty much do anything from subpoenaing witnesses and documents to appointing it’s own Special Counsel and, basically, conduct its’ own investigation.
Given Brett Kavanaugh’s lies, perjuries, and the attempted rape allegations now in the news, it seems to be that all of that...everything... is fertile ground for an impeachment inquiry...provided Democrats win the House of Representatives…and even if Brett Kavanaugh is confirmed as a Supreme Court Justice by the United States Senate.
Just...keep that in a file in the back of your mind.