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?
In my opinion, the phrases:
So, I don't think the word 'the' is overused.
Being strict, it depends on context.
If this message is an instruction provided before any results have been presented, then "the results" doesn't quite make sense because "the" is the definite article. That means "the results" refers to a specific set of results. Which specific results? If results don't already exist, it's not clear. I'll likely assume you're talking about "the results [of the next search]". I'd be right, so you'd still be communicating successfully, but it's not ideal.
On the other hand, if the message doesn't appear until after a search is performed and some results (especially a large number of them) are presented, it would work perfectly because "the results" refers to a specific set of results that exist in context.
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.