How do you add a hand held spray head to existing shower head?

Swap out current showerhead for a hand held model. The link provided is just an example of what to look for.

You can buy them at Home Depot. I bought a shower head that was a 2-in-1 shower head, it was a shower head that was held on by a magnet so you could remove it & use it as a hand held. I saw another option to buy just the hand held where you remove the existing shower head to insert the hand held attachment & replace the existing shower head.

You will need a new showerhead. I don't know of any way to convert a standard showeeheas

You just screw the old one off and screw the new one on.

Have had a Shower Massage for about 35 yrs. and I love it. They don't seem difficult to install.

You just screw old one off and screw the new one on.

Seems you want both and not just the hand held. I also have both. I like the showerhead, my son like the hand held (he's too tall for the showerhead) What you are looking for is a hand held shower T-diverter so you can have your regular showerhead and a hand held at the same time. The diverter has a lever to switch between the showerhead or hand held. I know Walmart sells them starting at $9 +. Ace Hardware, Menards, or Lowes also. Here is a link for Home Depot as an example.