how do I find the correct verb
Quien banarse primero?
2 Answers
Quien is 3rd person singular here, so it would be "¿Quién se baña primero?"
Look on the More tab and you will find a conjugator for all verbs.
You could say this in simple future tense "¿Quién se bañará primero?" but it´s not common usage in this situation.
See video lesson 2.5 on how to use reflexive verbs for your morning routine.