Van Dijk helped Liverpool recruit Wirtz from Bayer Leverkusen at the beginning of the summer.
The Reds skipper said from Liverpool's preseason base in Hong Kong: "When I joined the club I said it, I don't think there's a better place to be than Liverpool.
"I really feel that way. We had a fantastic season and I feel like this can only become better.
"When Florian spoke to the club and certain players, I spoke to him as well a little bit, I'm sure he got a feel for it. And then he made a decision.
"Coming here, he can really make an impact in my opinion. But it's also down to him in terms of showing it every single day. He's getting there and it's good to see.
"I said to him, 'Liverpool is the place to be'."
You need to show your quality
On defending their Premier League title, Van Dijk has warned teammates - including Wirtz - and fans there are "no guarantees".
He also stated: "The message is 'the hard work starts now'. That's it. You're playing for one of the biggest clubs in the world now. The pressure will be on you. You need to show your qualities.
"Listen, there are no guarantees in terms of retaining the title or winning more trophies.
"But improving the squad is always a good thing. Adding quality helps to raise the standard in both training and games hopefully. We've all seen it over the years, the team which is the most consistent during the season wins titles, and that's the aim we have.
"We want to show our quality in every single aspect of the game. That's a very tough job. If it was easy then you'd have a lot of teams up there until the end."