The story is fairly simple: there is a museum about the titular wizard, and part of the exhibit is you can pay to spend time with a basic set of arcana, a.k.a. spells or skills, where you go through a small recreation of what a chaos trial may have been like. At the end, you touch a monument, and you are unexpectedly magically transported to a new place where you have the chance to actually become a real Wizard of Legend by partaking in the actual Chaos Trials.
Source: N4G PC Wizard of Legend review – ChristCenteredGamer