I am a native speaker of [Spanish, Portuguese, French]. How should I handle the language evaluation?

As a native speaker, ask the relevant language department at your institution if someone there can do a quick assessment, and then designate that person as your recommender via the online application system. Alternately, if you have used the language in the workplace, or as a volunteer, or if you have taken courses taught in the language, ask your instructor or work supervisor to serve as a language evaluator. While the online application has space for the language recommender to submit a letter of recommendation, that is optional. However, they must complete the questionnaire that is part of the language assessment.