Should I apply for a position to be a B2B sales professional? How to emphasize my strengths and potential?

A cover letter should be ideally written on one page. You may include your actual qualification and experience in the resume. However, in the cover letter put more emphasis on how you fit the employer's wish of an ideal candidate for the job. Tell what you are capable of doing for him, highlight your achievements that can be related to the current opportunity. Good luck!