I bought a house in connecticut in 2016 and I received a form OP-236. I have no idea what to do with it

This has nothing to do with Federal Income Taxes but it does apply to the state. Below are several links explaining it.  You may also call the state at 1-860-297-5962.

http://www.lawcts.com/connecticut-real-estate-conveyance-taxes/

http://www.ct.gov/drs/lib/drs/forms/2008forms/excise/realestateconveyance/op-236i.pdf

www.ct.gov/drs/lib/drs/forms/1-2016/excise/op-236i.pdf