Ich bin eine IT-affine Person.
is correct. In German compounds, there is either a hyphen or nothing between the elements.
- In no case there is a space as in English. Though, a lot of people are doing this wrong, even on public displays. Most of them are excused for being second language speakers of German. There's even a name for this bad habit, it's called Deppenleerzeichen – dork space.
If there are multiple proper names connected, or if there are abbreviations inside the word, all parts must be connected with hyphens. This is called Durchkopplung.
Ich bin eine Microsoft-Apple-Linux-affine Person.
Ich bin eine mobil-IT-affine Person.
Though, your expression doesn't mean what you may think in German. Most people would assume an IT-affine Person is someone who is always buying the latest stuff, not necessarily knowing how to use it. It's part of your lifestyle, not part of your profession. Think Aficionado.
If you think it's part of your profession, you should write
Ich kenne mich gut mit IT aus.