A cover letter aims to convince the recruiter that you are the best possible candidate. It is the document used to pitch yourself and land the job you want, and it is as vital as your resume. The main difference being you can use the cover letter to further explain why you want the job and what you can bring to the company (skills, experience, qualifications, etc.).
You will need a salutation; knowing the recruiter’s name is good practice. If you can research and find this out, then it will put you ahead of the pack. Otherwise, you can open with Dear Recruiter/Hiring Manager. After this, you will need an introduction, middle paragraph(s), and a final paragraph. Don’t forget to sign off with “Sincerely” or “Best Regards” and your name.
If you have little or no experience, then you can modify your cover letter to suit what experience you have.
If you have experience as a caseworker, then this is a great start. If not, then you can feature volunteer roles as examples of work experience, and refer to this in the cover letter. You can start volunteering for a relevant charity or non-profit organization and apply for trainee caseworker/handler positions.
Alternatively, if you have a caseworker background and want to step up to a management role, you can state this career goal in your cover letter and resume.