Which language skills are most important for your application depends on the job you're applying for.
You should check whether knowing a language is a key requirement by reviewing the job description. If knowledge of a language that you speak is a requirement then highlight that language in your CV.
You can highlight important language skills in:
your personal statement
a separate languages section
your key skills section
Remember that where on your CV you decide to include your language skills will influence how likely the employer is to notice them.
Including language skills high up on your CV or in a separate section will make them more visible but also takes up space that you could use to showcase other valuable skills.
Think about how important the language is to the job you're applying for, and list the language in an appropriate section.