Question: For some reason I feel its overkilling on the use of article(the) here, 

> 
> To refine the results, please use the categories on the left
> 
> 
> 

Can someone help?

Answer: 
As others have said, your sentence is fine, as-is.

However, you might change it to "To refine *your* results, please use the categories on the left."

This would mitigate your concerns with the repeated "the".
Technically, the sentence is correct but the is overused. I would rearrange the sentence to say "Refine results using the categories on the left". It removes a couple of words and also makes it a more active sentence. Also when writing instructions, avoid using please. These are instructions for performing a task and not a request so the word please is not necessary.