I need some help...

So I had just turned 14 in April and my gf (who is gonna be 17 this year and she is mtf transgender yes she has a penis if u were gonna ask) wanted me to come over after we celebrated my bday and spend the night. Now my parents don't know that I'm not a virgin any more and that she took my virginity a few days after christmas and that I'm a bisexual girl. So I get to her house and she is home alone what I didn't know was that she had something set up for me. We had sex and skip about an hour and a half later. The thing I wanna know is how can I tell my parents about me being a bi and ab my sex life?

Edit:for that person who commented that I'm to young for this and that shes to old for me we've been dating for 2 almost 3 years now just to clear that out.