If you have been refused before, you have probably been told two things, both wrong: that you should wait a while and try again unchanged, or that you should not mention it.
Do not conceal it
A refusal is recorded. The next officer is likely to see it, and application forms generally ask directly. An application that omits a refusal it was asked about is no longer a weak application — it is a dishonest one, and that is a far harder position to recover from than the original refusal.
Understand what was actually refused
A refusal notice usually gives a reason, often in standard wording. That wording matters: a refusal for insufficient evidence of funds is a different problem from a refusal for doubt about your intention to return, and the second is not solved by adding money to an account.
Change something real
Reapplying with the same file invites the same answer. Something in the application has to be materially different — better evidence, a clearer purpose, a stronger tie to home, a more realistic destination or timing. If nothing has changed, we will say so rather than take a fee to resubmit the same file.
Then say so plainly
A second application that acknowledges the first, explains what has changed and evidences it, is a normal and entirely respectable thing to put in front of an embassy.
If you have a refusal behind you, say so at the assessment. It is the single most useful thing you can tell us.