I am sorry this happened to you.
I would advise doing this only if you want to or think it will be beneficial to you. Hopefully your therapist is not pushing you into this decision.
I don't know how helpful this will be, as I have to keep it vague and I'm in the U.S.
First, I would be aware of the statute of limitations in your area.
I called the station where it happened and drove to that state to make a report to regular police.
They passed it on to the detective who called me back the next week.
I went up to his station to give a videotaped interview which lasted a couple hours...they will ask very intrusive and sensitive questions and it may seem like they're trying to poke holes in your story or don't believe you...like a mini-cross-examination.
Then, once you're done, they will lay out the options you have. I was given a choice of whether to go through with the option or not.
A lot of options will depend on how long ago it was, whether there remains any physical evidence/DNA, etc.
For what it's worth, I did not have an advocate with me and I was reporting things from a loooong time ago, plus the detective told me he didn't like me because of my taste in music and because at the time I was a cigarette smoker. He also did not prepare me adequately for what I had to do as my next step (which I can't revel here). He was also...very forthcoming with depressing statistics and vague examples of people who got out of charges with ridiculous loopholes. It was really quite discouraging, but that is...an unfortunate reality.
Whatever you choose, I hope it works for you.