First, you must die. This is not as easy as it seems, because you must die in a specific way. You have to die for your religion, while also in a way that stands out of other means of dying for your religion, so suicide bomber is right out. You have to die peacefully, preferably in a non-violent way when faced with a situation of extreme violence, or when violence would save your life but hurt others. You must also have lived a good and fruitful life so you can pass onto heaven (and so that people know of your good deeds).
Afterwards, the hard part starts. You end up in heaven, and you must immediately fill in formula 4D to 4P when entering, to even allow you to be able to apply for a Saint position. You have to ask about it yourself, there is nothing at Saint Peter's place that can remind you of it. If you forget this step, too bad. Reincarnate and die again (for reincarnation, you have to go to the Divine Saecretary, ask for Raphael and mention my name, he'll help you out). If you did fill out the forms, you must wait for a reply. Generally, this takes between 2 to 15 years.
When you get the reply, go to the Santrificus Divinata and request an audition with God himself. It will be refused and you will be pointed towards Gabriel instead, who has taken over for God almost full-time (just don't let the topic get to that or you'll still be sitting there a year later, and still haven't heard all of his complaints). Ask him for a permit to perform miracles, and to take miracle lessons. You will have to fill out forms 7 A and C, 40 O, M and G and 3 D, each three times, and hand them in at the Miracle School (forms 7), the Gateway To The Outer World (forms 40), and finally the Miracle Performer Cannon Station (form 3).
Shortly afterwards (about 4 years), you'll get a reply from all of them. If you have been found good enough, you will start attending miracle lessons for 40 to 120 years, depending on how good you are. Then you have to go to the Gateway To The Outer World, ask for form 2 B, fill it in, send it to Hell's Bureau Concerning Nice People and await it's reply saying that you aren't in any entry of Hell's Database. If you kicked a puppy once (or the like), you will need to reincarnate and try again (see above for instructions).
Then, finally, you can go to the Miracle Performer Cannon Station and use the Miracle Performer Cannon once. For the second miracle, you will have to wait 7 years. After performing your second miracle, you will have to wait until the Human Church recognises both of your miracles and make you a saint.--El_Nazgir