I tried to knit a scarf using knitting for pom Pom method but it just don’t look right. Do I use a bigger needle?
Welcome to KH!
You could certainly try larger needles but it y not help. The size of the sts becomes limited by the spacing of the pom poms rather than the needles.
If you have enough yarn you might see if doubling the yarn will work to give a fuller look to the kntting.
Sometimes yarn like that is hard to knit. I’ve seen people carry another plain yarn with it to give it a fuller look, too.