Points to note:
[1] Arabic is the language the Quran was revealed in.
[2] Allah is the Arabic word for God.
[3] You are in essence affirming in your heart that God is the only one truly worthy of worship and that Muhammad (and nobody else) was the person who came to teach us how to worship God. That’s why as Muslims, we revere Muhammed and follow his teachings – whilst still appreciating he is still human and not divine.

In more detail:

The word “Muslim” means one who submits to the will of God, regardless of their race, nationality or ethnic background. Becoming a Muslim is a simple and easy process that requires no pre-requisites. One may convert alone in privacy, or he/she may do so in the presence of others.
If anyone has a real desire to be a Muslim and has full conviction and a strong belief that Islam is the true religion of God, then, all one needs to do is pronounce the “Shahada”, the testimony of faith, without further delay. The “Shahada” is the first and most important of the five pillars of Islam.
With the pronunciation of this testimony, or “Shahada”, with sincere belief and conviction, one enters the fold of Islam.
Upon entering the fold of Islam purely for the Pleasure of God, all of one’s previous sins are forgiven, and one starts a new life of piety and righteousness. The Prophet said to a person who had placed the condition upon the Prophet in accepting Islam that God would forgive his sins:

When one accepts Islam, they, in essence, repent from the ways and beliefs of their previous life. One need not be overburdened by sins committed before their acceptance. The person’s record is clean, and it is as if he was just born from his mother’s womb. One should try as much as possible to keep his records clean and strive to do as many good deeds as possible.
The Holy Quran and Hadeeth (prophetic sayings) both stress the importance of following Islam. God states:

In another verse of the Holy Quran, God states:

In another saying, Muhammad (peace be upon him), the Prophet of God, said:

The Prophet of God, may the blessing and mercy of God be upon him, also reported:

The Declaration of the Testimony (Shahada)

To convert to Islam and become a Muslim a person needs to pronounce the below testimony with conviction and understanding its meaning:
I testify “La ilah illa Allah, Muhammad rasoolu Allah.”
The translation of which is:

When someone pronounces the testimony with conviction, then he/she has become a Muslim. It can be done alone, but it is much better to be done with an adviser through the “Live Help” at the top, so we may help you in pronouncing it right and to provide you with important resources for new Muslims.
The first part of the testimony consists of the most important truth that God revealed to mankind: that there is nothing divine or worthy of being worshipped except for Almighty God. God states in the Holy Quran:

This conveys that all forms of worship, whether it be praying, fasting, invoking, seeking refuge in, and offering an animal as sacrifice, must be directed to God and to God alone. Directing any form of worship to other than God (whether it be an angel, a messenger, Jesus, Muhammad, a saint, an idol, the sun, the moon, a tree) is seen as a contradiction to the fundamental message of Islam, and it is an unforgivable sin unless it is repented from before one dies. All forms of worship must be directed to God only.
Worship means the performance of deeds and sayings that please God, things which He commanded or encouraged to be performed, either by direct textual proof or by analogy. Thus, worship is not restricted to the implementation of the five pillars of Islam, but also includes every aspect of life. Providing food for one’s family, and saying something pleasant to cheer a person up are also considered acts of worship if such is done with the intention of pleasing God. This means that to be accepted, all acts of worship must be carried out sincerely for the Sake of God alone.
The second part of the testimony means that Prophet Muhammad is the servant and chosen messenger of God. This implies that one obeys and follows the commands of the Prophet. One must believe in what he has said, practice his teachings and avoid what he has forbidden. One must, therefore, worship God only according to his teaching alone, for all the teachings of the Prophet were in fact revelations and inspirations conveyed to him by God.
One must try to mould their lives and character and emulate the Prophet, as he was a living example for humans to follow. God says:

God also said:

To truly adhere to the second part of the Shahada is to follow his example in all walks of life. God says:

We welcome you to Islam, congratulate you for your decision. You’re a Muslim Now. So what happens next? Where do you go from here? Check out iERA’s new Muslim programs dedicated to welcome, empower and provide education for New Muslims.