The academy enrolled twice per year, and there were only three methods one could use to enter:money, connections, and strength.
The person could either pay an exorbitant sum of money and precious materials, have a personal connection with one of the heads of the academy, or simply win a competition set up by the academy against other students.
It was needless to say, the option Ainz picked was the third one, of course, he could have picked the first, but that would have been too troublesome since he would have to go around killing magical beasts to earn money, but that wasn't what he found to be troublesome it was the fact, he had no idea how much he needed to pay to get himself enrolled, so he simply gave up the first two options.
