Gareth Jenkins's men kick off their campaign against Canada in Nantes on Sunday and over 20,000 fans are expected to travel.
Popham said, "Since the England game, things have improved massively and that's the way we want it to continue. We just want everyone behind us now. It does make a massive difference.
"We want support all the way through. I know the press have been negative and the public hasn't been happy. We know we didn't perform at Twickenham, we got beat heavily and we had a lot of criticism after that.
"But we know from the last two games we've played that everything is going in the right direction. It's about keeping that going and getting the results.
"The boys say they don't read the papers but sometimes you do and if you see something good about yourself, it's only going to help. Everyone is entitled to their opinion. But you want to be feeling positive, because otherwise it's going to affect your game.
"If you do go into this tournament thinking you are a decent player, then it's bound to help. We want some positive feelings going into this."
The Welsh squad have been together for nearly three months now with extensive preparations for the tournament and No.8 Popham says they are itching to get started.
"The 12 weeks seem to have gone quite slow," he said. "There were some days you were doing so many squats you could hardly walk. It was really intense.
"We've worked really hard, but we are all in good nick physically as a result. Personally, I've put on about five or six kilos since starting pre-season and we are coming out of it now fresh.
"The boys are fit and strong and we can't wait to get out there and play on Sunday."