I Have Naturally Wavy Hair. How Can I Make My Hair Curlier?

You could use a curling iron on your hair.

Add mousse after you've washed it, then scrunch it in your hands as you dry it. Don't use a brush, or your hair will go frizzy.

Get a permanent from a qualified hairdresser

Cut it shorter. I have wavy hair and it was terrible for a while. Then I cut it shorter and now its amazing!!

I have wavy hair, but I really like it when it is curly, so this is what I do:
Wash my hair with shampoo and conditioner
make sure it all gets washed out
take your towel and squeeze some of the water out of your hair. Be careful not to frizz it
hang your hair upside down, run your fingers onto your scalp from your face
shake out your hair from the roots, but the roots only. Be a little rough
take some curling mousse and apply a medium amount, scrunching hair as you go along. The mousse isn't necessary, but I like to use it
take your hair dryer with the diffuser head on it and turn to low power high heat
gather hair into the dish shape diffuser and put flat against head for 10 seconds
do this with the whole head
then turn it to medium heat low power and do the same thing until you hair is reasonably dry
throw your hair back and let the rest dry naturally
when I do this, I find I end up with cork screws at the bottom of my hair
I have layered thin hair, and it works with me
hope this is of use

You can make your hair curlier by slicking conditioner on your hair as soon as you get out of the shower. Or you can buy hair rollers. When using hair rollers you roll your hair upwards. The next morning, take out the rollers and brush out your hair. You might want to put on hair spray when applying rollers.