Become Muslim first, then do not worry about your past
Question

i'm a young girl, wanting to convert to islam, for me this religion is really the truth. The problem is, that before i discovered islam, i used to live a pretty wild life, I did a lot of wrong things (if not all wrong things). I would like to know if it's possible for a girl like me to convert, and what should I do regarding my past when converting
Praise be to Allah.In the name of Allah, the Most Gracious, the Most Merciful 
“The revelation of the Book (this Quran) is from Allah, the All Mighty, the All Knower.
The Forgiver of sin, the Acceptor of repentance, the Severe in punishment, the Bestower (of favours). Laa ilaaha illa Huwa (none has the right to be worshipped but He), to Him is the final return”[Ghaafir 40:2-3 – interpretation of the meaning]
 Ibn ‘Abbaas – who was one of the companions of the Prophet of Islam (peace and blessings of Allah be upon him) – narrated that some of the people of shirk (polytheism) killed and did a lot of killing, and they committed adultery and they did that a great deal, then they came to Muhammad (peace and blessings of Allah be upon him) and said, “What you say and what you are calling for is good. If only you could tell us that there is any expiation for what we have done.” Then Allah revealed the words (interpretation of the meaning):
‘Say: “O ‘Ibaadi (My slaves) who have transgressed against themselves (by committing evil deeds and sins)! Despair not of the Mercy of Allah, verily, Allah forgives all sins. Truly, He is Oft‑Forgiving, Most Merciful.
And turn in repentance and in obedience with true Faith (Islamic Monotheism) to your Lord and submit to Him (in Islam) before the torment comes upon you, (and) then you will not be helped.
And follow the best of that which is sent down to you from your Lord (i.e. this Quran, do what it orders you to do and keep away from what it forbids), before the torment comes on you suddenly while you perceive not!”
Lest a person should say: “Alas, my grief that I was undutiful to Allah (i.e. I have not done what Allah has ordered me to do), and I was indeed among those who mocked [at the truth! i.e. Laa ilaaha illAllah (none has the right to be worshipped but Allah), the Quran, and Muhammad and at the faithful believers]
Or (lest) he should say: “If only Allah had guided me, I should indeed have been among the Muttaqoon (the pious).”
Or (lest) he should say when he sees the torment: “If only I had another chance (to return to the world), then I should indeed be among the Muhsinoon (good‑doers).”
Yes! Verily, there came to you My Ayaat (proofs, evidences, verses, lessons, signs, revelations, etc.) and you denied them, and were proud and were among the disbelievers.’[al-Zumar 39:53-59]”
 ‘Amr ibn al-‘Aas was a mushrik (polytheist, idol-worshipper), a sinner and an enemy of Allah. He said: “When Allah put the love of Islam into my heart, I came to the Prophet (peace and blessings of Allah be upon him) to pledge my allegiance to him. He stretched out his hand towards me, but I said, ‘I will not pledge allegiance to you, O Messenger of Allah, until you forgive me my previous sins.’ The Messenger of Allah (peace and blessings of Allah be upon him) said to me, ‘O ‘Amr, do you not know that Islam wipes out whatever sins came before it.’” (Narrated by Imaam Ahmad, 17159). 
So flee to Allah and know that there is nothing that you are worried about, but the solution to it is to be found in the texts quoted above. Indeed, these texts are addressed to you; they refer to your situation and contain the answer to your problem.
 Your Lord is Most Merciful; He accepts repentance and forgives all sins. His Mercy encompasses all things. He calls you and all His slaves to repent and to become Muslim. He has promised you, through the words of His Messenger (peace and blessings of Allah be upon him), that all of your previous sins, major and minor, of whatever type, will be wiped out completely when you become Muslim, and you will start with a clean sheet, a new record of deeds that is free of bad deeds. So what are you waiting for? Why delay it any further? Hasten to enter Islam and worship your Lord, and we give you the glad tidings of a happy future and a good life in the shade of Islam. We were very happy – by Allah – to receive your question, and we are waiting to hear good news.
 For more information on how to enter Islam, please look at Questions :  703 & 49715  And Embracing Islam . May Allah protect you from all evil, for He is the Best of Protectors and the Best of Supporters, and He is the Guide to the Straight Path.