This information should be clearly stated on your resume as part of the section it is attached to. For example, if you are creating resume bullet points for an internship in which you translated documents, this should be a main point and as descriptive as possible:
Translated medical records for over 50 patients from original source and language, (French to English) in writing and provided cultural context (Haitian) to nursing staff.
If you used your language skills as an everyday part of your job outside of an actual task, such as communicating with coworkers or customers, consider adding a bullet point to your resume and then explaining this in more detail in your cover letter.