Change from sole ownership to joint ownership. Filling in CGT form after sale

I have recently sold a property I bought as a sole owner in 1984 Last year my husband became a joint owner with me. I am trying to fill in the CGT forms but I am having difficulty finding the relevant place to put this information. Thanks very much.

Hi,
You will report the sale as 50% rather than 100%, and your husband will do the same.
Thank you.