how to start playing?

what do you mean “start playing”?

he playes when he wants too

You can really bond with your kitten by playing with him, and it helps him learn coordination and helps tone his muscles too. Often if you just dangle something small and harmless and let him bat at it, or chase it across the floor on a string, he can be happy for ages. (Be sure to let him catch it sometimes; he needs to be rewarded for his efforts.)

The first article I’m linking to is an excellent article about the types of play, and how to do it. [At least...I think I'm linking to it. It's not showing up when I'm in the "Confirm" phase of posting this, so I hope it shows up when it finally posts! Otherwise I'll make another post and put the links in the body of the post instead.]

The author makes a good point about trying to keep your hands and arms away, even when playing “attack.” (He suggests always using an inanimate object, so the kitten isn’t taught that it’s okay to attack you directly.) I’ve heard that it’s possible to train a kitten by tapping it very softly on the nose if it’s done something it shouldn’t, and saying a firm but not-too-loud “No.” I haven’t had a chance to try that myself, so I can’t say for sure how it turns out.

The second article is also about play, but has even more info about helping a kitten learn not to play too roughly.

Source Link: How to Play with a Kitten
Source Link: Managing Your Kitten\’s Rough Play

A way to know when your cat starts to play, is when it will start to mess with stuff!! Like maybe some string or something he/she like alot like a toy, or someting!! This is a kind of difficult question to anwser!!

Try to bond with him and get a toy ball and/or a mouse and start to play

Source Link: cats