Alhamdulillah, you're considering Islam as way of life, a righteous path to follow and a new belief system.
If this is true, we congratulate you as you journey closer to Allah(Swt), seeking as much knowledge and spiritual guidance as you can.
The implication of the Shahada is that you believe that there is only one God, Allah (God in Arabic), Who alone deserves to be worshiped and you believe in Muhammad, peace be upon him & his family, as the Last Messenger of God, and you believe in his message.
It also means that you believe in all of God's Prophets, including Jesus, peace be upon him, who is a Messenger of God but he was not divine or the son of God.
You may be surprised to hear that becoming a Muslim takes only seconds but when you confess you will have to know, in your heart, that this new way of life is the direction you wish to follow.
This is a momentous moment in your life, not one you'll surely forget. When a new Muslim takes his/her Shahada (Translation: witnessing) they can recite it alone under God or at a Mosque (Masjid) in a kind of ceremony. However you recite your shahada it will be emotional and your life will forever change.
At the Revert Muslims Association we can make arrangements to help you find Muslims in your neighbourhood, so that you can confess at the mosque or with new friends. We can also make arrangements to reach you online, over Skype, should you wish to have help in pronunciation of the Shahada or simply wish to have a witness.
Keep in mind, you are perfectly fine to do your shahada at home, alone.
The Shahada is as follows:
"La ilaha il Allah, Muhammad-ur-Rasool-Allah"
(None has the right to be worshiped but Allah, and Muhammad is the Messenger of Allah)
The following may be added if you wish to declare that you have consciously decided to accept the Ja’fari school of thought :
Ash-Hadu Anla Illaha Illa-Alllah, wa Ash-Hadu Anna Mohammedan Rasul-Ullah.
wa Ash-Hadu An Amiree-ul Momineen wa Imam Al Mutaqeen, Ali an Wali-Ullah, Wasiyeh Rasul-Ullah, Wa Kalifatahu Bila Fasl.
(I testify that there is no God but Allah, and I testify that Mohammed is his Messenger, and I testify that the Commander of the Faithful, the Pure Leader, Ali, is the friend of Allah, the successor of the Messenger of Allah, and nothing can come between them.
The shahada is the Muslim profession of faith, expressing the two simple, fundamental beliefs that make one a Muslim:
Sincere recitation of this confession of faith is the sole requirement for those who wish to join the Muslim community. It represents acceptance not only of Allah and his prophet, but of the entirety of Islam. As one of the Pillars, the shahada must be recited correctly aloud with full understanding and internal assent at least once in every Muslim's lifetime.
The shahada is also recited in the muzzein's call to prayer, included in the salat (daily ritual prayer) and incorporated in Sufi contemplative prayer. It is also recited in the moments before death.
What should I do after becoming a Muslim?
Immediately upon becoming a Muslim, you should take a bath or shower (i.e. Ghusl).
If able, you should then offer a two Rak’at prayer.
Then you must study and act upon the principles (pillars) of Islam, (Shi'a and Sunni Islam are slightly different).