The song is on this National Institutes of Health Kids Page. 

How to Do the Hokey Pokey

• Stand in a ring. A leader names the body parts, for example "left leg," and these are put in the ring, taken out of the ring, put in again and energetically wiggled around.
• Then raise hands above the head, wiggle them and turn around in place until the next body part is called out.

Here's a sample:

• You put your left leg in
• You put your left leg out
• You put your left leg in
• And you shake it all about.
• You do the Hokey Pokey and you turn yourself around.
• That's (clap) what (clap) it's all (clap behind back) about (clap above head).

You and your child can make up your own words and movements to accompany music you enjoy.