Headspins are a tough move that you shouldn't try as a beginner. They are a pain to learn because of the time it takes to train your legs to stay straight in the move. It is also a move that you lose if you don't practice and maintain it.
Step 1 Find your balance spot on your head
When you are in a headstand move your chin away and close to your chest, this will move your balance spot from the back of your head to your forehead. You will find that spot where it feels comfortable and stable. That is your balance spot.
Step 2 Mastering Being on Your Head
Get used to being on your head for 30-90 seconds. Then get used to kicking your legs and never falling over. You have to dominate the headstands so you never fall.
Step 3 Rotating
After mastering the headstand you will start walking yourself around in a circle keeping your legs straight, above your hips and in a split position. Once you can walk yourself around like that then you do quarter, half then full rotations.
Not being on your balance spot
Legs falling below the hips
Not maintaining the split position.
If you find yourself falling a lot watch yourself on video and look at your legs. Its usually your legs not being symmetrical that will make you fall.
It takes about two months to master the headstand. Then a couple of months to master headspins. Its best to practice small amounts around 15 minutes more frequently than long hour long headspin training sessions.