Sir Tydus is standing right beside Armin Saberlin. This is the final step you take in the Pre-Searing version of Ascalon: accepting the reward for this quest will allow your character to leave the small, safe world they have come to know and journey through the events of The Searing. Once you accept Sir Tydus' request to enter the Academy, the character will not be able to return to the Pre-Searing world, so ensure you have done everything you want to accomplish there first.