To soften the cream cheese and butter, just leave it sitting out (in the package or covered) on your countertop for a couple hours. During colder months, I sometimes will leave them out overnight to use the next day.

In a stand mixer (or an electric handheld mixer), combine the cream cheese, butter, and vanilla extract. Beat with the whisk or paddle attachment until well combined. Use a rubber spatula to scrape down the sides of the bowl. Now add the powdered sugar, stopping the mixer and scraping down the sides of the bowl as needed until everything is combined. Lastly, mix in the peanut butter. You only need to mix until combined; you can even fold the peanut butter in by hand with the spatula at this point if you like.