Gakpo contributed a goal alongside strikes from Mohamed Salah, Dominik Szoboszlai, and Virgil van Dijk to overturn a first-leg deficit at Anfield.
Liverpool will now face Newcastle United in the final at Wembley on March 16, aiming to secure the trophy.
"We are on the right track," Gakpo reflected to Sky Sports post-match.
"We have to take it game by game and step by step.
"Today it's a good job done. We are in one final, but we have a lot to play for still. We have to stay calm and focus to reach as much as possible."
On the comeback, he added: “I think the stadium helped a lot. We knew we had to come back from 1-0 behind. We went out there and tried to bring as much chances as possible.
“With the quality we have, we know we are going to get big chances and hopefully score. That happened and (it was) a very good performance I think from the whole team. It was a great win.”