How/Where to Install chlorinator

[rtpatter]

I know that on this board chlorinators are viewed as bad and I will still primarily use bleach however I would like to ditch my floater that I use and install a chlorinator. However, based on my setup I wasn't sure how/where to install one or if I should just hire it done. I attached a photo. I think where I would need to install one would be right where the two paint drop stains are close to the polaris booster pump. I think that is the return line. However, I don't think I have enough room in the line to install an inline chlorinator. Therefore, do I need an offline chlorinator? Also do I need a backflow valve to prevent fumes from backing up into my heater?

Any advice appreciated