How a secured card works
You put down a refundable deposit — often $200 — and that becomes your credit limit. You use the card like any other, and the issuer reports your payments to the three bureaus. The deposit just protects the lender if you don't pay; it isn't a fee.
After six to twelve months of on-time use, many issuers refund the deposit and graduate you to a regular unsecured card.

Use it so it actually helps
Charge one small recurring bill to it — a streaming subscription, your phone bill — and set up autopay for the full balance. That reports on-time history and keeps utilization low without any risk of carrying interest.
Keep the balance you let report under about 10% of the limit. On a $200 limit, that's keeping the reported balance under ~$20.
Choose carefully
Pick a card that: reports to all three bureaus (most do, but confirm), has no annual fee or a very low one, and offers a path to graduate. Avoid 'fee-harvester' cards that eat your deposit with setup and monthly fees.
A secured card is different from a prepaid or debit card — only cards that report to the bureaus build credit.
What to expect
A thin-file consumer often sees a usable score appear within about six months of on-time reporting. It's not instant, and the deposit ties up cash, but it's the most dependable first step.
Secured cards, rent reporting, and becoming an authorized user all add positive history from zero. Subefy matches you to cards you're likely to be approved for and tracks the on-time months. Results vary and approval isn't guaranteed.