The phrase "to use the key" means to employ or utilize a specific tool or method that allows access or understanding to something important or valuable. Full definition
These vocabulary strategies help students build their comprehension and language skills by using key words from Perspectives texts in their own reading, writing, speaking and listening. (tolerance.org)
When writing your CV, you can maximize your chances of being considered for an available position by using key terms in your document, especially in your skills section. (resume-now.com)
Establish your suitability for the role by using the key terms in your professional summary, work experience, and skills section, with an emphasis on your accomplishments. (resume-now.com)