Certainty in Islam and in Allah and all the Prophets, peace and blessings upon them all, needs to come from within.
It comes from the heart, soul and mind. I don't think it's something we can teach.
What you can do is sit in contemplation and look at the human anatomy, look at how our body functions effortlessly, with all it's amazing organs. If you've got time after this, you can look at the animals, your surroundings, the world we live in, how the moon shines so brightly at night, the light of the sun and so on.
Have you read and understood Allah's message by reading the Quraan?
Allah swt talks to us directly through the scriptures so your yaqeen, your certainity, may come by understanding the Quraan?
You might be interested in the below article;
Aqeedah refers to those matters which are believed in, with certainty and conviction, in one’s heart and soul. They are not tainted with any doubt or uncertainty.
The principles of ‘aqeedah are those which Allaah has commanded us to believe in, as mentioned in the aayah (interpretation of the meaning):
"The Messenger believes in what has been sent down to him from his Lord, and (so do) the believers. Each one believes in Allaah, His Angels, His Books and His Messengers. They say, ‘We make no distinction between one and another of His Messengers’ – and they say, ‘We hear, and we obey. (We seek) Your forgiveness, our Lord, and to You is the return (of all).’" [al-Baqarah 2:285]
- and as defined by the Prophet (peace and blessings of Allaah be upon him) in the famous hadeeth which describes how Jibreel came to him and asked him about Islam etc.: "Eemaan (faith) is to believe in Allaah, His angels, His Books, the meeting with Him on the Last Day, His Messengers, and the Day of Resurrection."
So in Islam, ‘aqeedah refers to the matters which are known from the Qur’aan and sound ahaadeeth, and which the Muslim must believe in his heart, in acknowledgement of the truth of Allaah and His Messenger.
If you wish to read more please visit; http://islamqa.info/en/951