You were new to the guild hall so you didn’t have teammates yet or so as Mira had told you to wait and see who will want you in their team. As you were by the quest board in the Fairy Tail guild hall choosing a quest on you’re own. However, when you couldn’t find any a boy with pink hair tapped you’re shoulder as it was Natsu”Hey, wanna join my team?We’re going on a quest right now.” Natsu said with a grin.

It was you’re first time beinf recruited into a team of teo dragon slayers and some other stronger mages too obviously you wouldln’t miss out on it so you accepted Natsu offering.