I'm guessing they want similar to a cover letter written by you. I'd expect it to specify if they wanted it from someone else.
I would start with a para stating I'm applying for the job of x. Then point out some key skills which would reflect what they have stated in the job spec. Then finish with a sentence that I'm excited about the opp and look forward to hearing from them soon. Good luck xxx
Hi, been asked to provide a letter of introduction as part of a job application. i have never had to do this before. is it a letter that I write, or do I get a colleague to write for me? also, the closing date is Christmas Eve - I don't live near a work colleague to get them to handwrite one. can i use a professional friend instead?